wbs 4.1.2.2 pathfinder technologies specialist, x-37 final
TRANSCRIPT
WBS 4.1.2.2
Pathfinder Technologies Specialist, X-37Final Report
Milestone Deliverable
Contract NAS8-99060
September 30, 2001
Prepared for
Space Transportation DirectorateGeorge C. Marshall Space Flight Center
National Aeronautics and Space Administration
Prepared by
Science Applications International Corporation
6725 Odyssey DriveHuntsville, AL 35806
WBS 4.1.2.2
Pathfinder Technologies Specialist, X-37Final Report
Back2round
The X-37 vehicle is a technology demonstrator sponsored by NASA. It includes a number
of experiments both imbedded (i.e., essential aspects of the vehicle) and separate. The
technologies demonstrated will be useful in future operational versions as well as having
broad applications to other programs. In the longer view, X-37 is intended to demonstrate
the capability of an orbiting vehicle with substantial propulsion capability to perform
missions both for NASA and USAF. X-37 will be placed in orbit by some launch vehicle
(some candidate vehicles require expenditure of some X-37 propellant) and will use the
majority of its onboard propellant for orbital operations. The Space Shuttle is the chosenlauncher for the first two missions. This will deliver X-37 to orbit with a full propellant
load. The X-37 is a winged vehicle with a "butterfly" tail. As far back as the wing trailing
edges, the planform is similar to the Space Shuttle Orbiter but the fuselage extends further
aft and mounts the two ruddervators that are the tail surfaces. This configuration is more
stable at high angle of attack than delta configurations such as Shuttle or X-33. These latter
vehicles tend to run away in pitch above a certain high angle of attack, meaning a risk of
flipping over. In the X-37 configuration, the tail surfaces come out of the wing shadow as
angle of attack increases resulting in a pitch down tendency.
Task Results
Mr. James R. French, of JRF Engineering Services and as a consultant to SAIC, has
provided technical support to the X-37 NASA Program Office since the beginning of the
program. In providing this service, Mr. French has maintained close contact with the
Boeing Seal Beach and Rocketdyne technical teams via telephone, e-mail, and periodic
visits. His interfaces were primarily with the working engineers in order to provide NASA
sponsors with a different view than that achieved through management channels.
Mr. French's periodic and highly detailed technical reports were submitted to NASA and
SAIC on a weekly/monthly basis. These reports addressed a wide spectrum of
programmatic and technical interests related to the X-37 Program including vehicle design,
flight sciences, propulsion, thermal protection, Guidance Navigation & Control (GN&C),
structures, and operations. During Option Year 1 (10/1/99 - 9/30/00), of Contract NAS8-
99060, Mr. French's reports were provided directly to sponsoring and management
personnel at NASA and SAIC. A summary of the Option Year 1 periodic reports was
provided to NASA as a milestone deliverable, "Pathfinder Technologies, X-37" dated
September 30, 2000.
This subjectmilestonedeliverableon WBS 4.1.2.2 is entitled "PathfinderTechnologiesSpecialist,X-37" and is datedSeptember30,2001. It is presentedin the following pagesasa consolidationof the twelve monthly reportssubmittedby Mr. Frenchduring OptionYear2 (10/1/00- 9/30/01)of thecontract. This report is submittedasanadjunct to theabove-mentionedsummaryreport for Option Year 1 and,as such,constitutesthe finalreportfor WBS4.1.2.2of ContractNAS8-99060.
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JRF ENGINEERING SERVICES
4023 Shadow Run
Las Cruces, NM 88011
(505) 532-9572 (phone/fax)
e-maih [email protected]
31 October 2000
To: Edgar W. NicksFrom: Jim French
Subject: X-37 Monthly Report
C: S. Turner. Lt. Col. Johannessen, M. Harris, J. London, B. Armstrong, S. Stewart, Maj.Titus
X-40A
Program Comment
It is difficult not to notice the high incidence of wiring damage plaguing the X-40A (see
G,N,&C below. It is possible of course to shrug this off as resulting from coincidence
however, that strains credulity to a degree. If the problem is systematic, it is difficult,
from this perspective, to say whether the cause is poor manufacturing and/or QA practice
or careless or inept work on the vehicle. If the various cables come from different
sources, that tends to reduce the probability that it is the manufacturing process and focus
attention on the work at DFRC. The delays from these sources are costing precious time
and putting the program at risk of greater delay. It might be worthwhile to apply someattention to this concern.
Flight Test
The condition of the lakebed continues to be an issue. Lakebed runway 25 was badly
rutted and torn up by C-17 tests. The Flight Test Center repaired the runway to the point
that they considered it suitable for the large aircraft that they normally operate. There was
concern that it might not be acceptable for X-40A with its small wheels and relatively
high speeds.
Some consideration was given to defining a surrogate "virtual runway" in the guidance
system. This would be physically located just north of and parallel to runway 25. Since
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X-37 Monthly Report October 31, 2000
Page 2
the X-40A has no depth perception problems, the lack of markings was not an issue and
the lakebed in that area looked fine. The rains eliminated that option.
I have been concerned for sometime about an early onset of the California winter rains;
we are moving into the southern California rainy season. The first rain occurred on 10
October. As a result, the lakebed became temporarily unusable. If there is no more rain
for a while, the lakebed will probably dry sufficiently for at least limited use. Exactly
when it will be fully usable again is TBD. As soon as it rains enough to accumulate water
on the lakebed, runway 25 will be out of action since it is at the low end of the lake. This
could happen any time. The other lakebed runways will be available for a while after the
rains start (probably) but eventually they too may be out of action. If we have a flight or
two under our belt when the lake becomes unusable, we may be able to talk the base
commander into allowing X-40A to use the paved runway. However, the probability of
being allowed to use it for the first landing is effectively zero. Thus, it is important to
move out smartly to get the first drop behind us.
If we lose use of the lakebed, White Sands Space Harbor may be an option but it would
require considerable effort to relocate the flights.
It is not clear exactly when the helicopter will be back because of various conflicts and
the need to get the proper blessings from DFRC concerning the computer and other
issues.
Training having been completed for the first free taxi tests, the free flight training is in
progress.
Taxi testing has progressed well. Towed runs were made building speed up to 45 mph.
When these went well, the team proceeded to free taxi tests. One release was conducted a
17 mph followed by four more at 27 mph. The Flight Computer worked well. There were
no uncommanded reboots nor did the computer hang up or lose telemetry. The tests went
well insofar as procedures and test equipment were concerned.
Some new issues did arise however (see G,N,&C below).
Vehicle Systems
The Flight Computer was tested by exposing it to an artificially created high rate
interrupts to verify that this causes a reboot. This test was done prior to the low speed taxi
tests. All this was done in concert with the software supplier, Wind River. Provision will
be made for storing data in the event a reboot does occur. The core memory will be
dumped following every normal run to verify no high rate interrupts. Methods of
protection are beingevaluated.
Software will be modified to deal with the Ethernet problem.
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JRF Engineering ServicesX-37 Monthly Report October 31, 2000Page 3
Moog has indicated that actuator life expectancy is not a problem. Boeing and
government personnel will want to review the results before a final determination is made
but it sounds promising.. This covers not only flight operations but the required testing
between flights. These tests are required to verify actuator condition prior to the next
flight.
Moog also identified a possible problem with regenerative power from the actuators. In
order to control the regenerative power, a 10,000 microfarad capacitor and a resistor will
be added to the power lines leading to the actuators to dissipate the generated energy.
Rewiring of vehicle circuits is in progress. The major efforts are the VRS repair, addition
of filters to the string potentiometer circuits, and replacement of the J-2 connector. These
changes have been discussed previously in connection with the anomalies encountered in
flight. The work also includes the actuator circuit changes discussed above.
The cables between the Flight Computer and C-MIGITS were inspected and tested by
flexing and twisting the cables to determine if any more shorts or other problems exist.
Upon conclusion of the rewiring, a series of checkouts will be run prior to resuming taxi
tests.
The test team continues to request a higher transmit power for Command and DGPS. The
request is somewhere in the DFRC approval cycle.
G_N_&C
On initial turnon for the taxi tests, the C-MIGITS did not see satellites and there was no
DGPS. However during a one-hour hold for another program, it began to see satellites
and by the time testing was resumed, DGPS was working. The C-MIGITs was found to
exhibit a 1 Hz oscillation in pitch and yaw. The amplitude was about + 0.1 degree. Since
the nosewheel steering uses yaw data from C-MIGITS, corresponding oscillations were
seen in the nosewheel steering commands and position feedback. Finally it was noted
that, during the test, the vehicle missed some uplink commands issued by the FOCC and
it was further noted that there was a delay between when a command was issued and
when it actually left the FOCC. These issues are being investigated. The EDU is in the
vehicle for testing at the moment and the team began looking for a flight-worthy loaner in
case the problem with the flight unit can't be fixed or takes too long to fix. A possiblecandidate loaner was identified.
The DGPS receiver is at the manufacturer for repair of a problem with the squelch circuit.
A representative from Radstone, the Flight Computer manufacturer, came to DFRC to
work on the computer problems. First was the reset problem. This had occurred three
times, once on the captive flight and twice in ground test. A second problem was the
computer suspending operations. It does this very repeatably in response to certain
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JRF Engineering ServicesX-37 Monthly Report October 3 I, 2000Page 4
conditions. Finally, he inspected the damage to the J2 connector discovered during
investigation in connection with the original reset problem.
It has been discovered that an excessive number of interrupts from C-MIGITS can cause
the Flight Computer to reset. It is not known whether this caused the problem
encountered in the captive flight but it is certainly a strong possibility (see below).
Unfortunately the flight telemetry does not report C-MIGITS interrupts so there is no
way to prove or disprove the speculation. The phenomenon was discovered in ground testwhere such data are recorded.
In connection with the above, investigation of the C-MIGITS problem resulted in
discovery of an intermittent short circuit in the cable connecting C-MIGITS to the Flight
Computer. The short tends to put noise on the line which looks very much like interrupts
to the computer. While we cannot know with absolute certainty that this has been the
source of the reset problems, the probability seems very high. The Radstone rep
apparently feels that this is the case.
The Radstone rep has also worked with the team in making some changes to eliminate
the hangup problem. With these changes made and the short repaired, the Flight
Computer has been running very well. At his suggestion, the J-2 connector with the
damaged faceplate will be changed. That is a very straightforward operation of moving
pins from one backshell to another. It is not even necessary to remove the cable from the
box. It appears that we can be cautiously optimistic that the computer problem is fixed.
The C-MIGITS used in the tests reported above was the unit borrowed from Long Beach.
As part of the investigation of the 1Hz oscillation, previous data were reviewed and itwas found that the EDU C-MIGITS had a similar oscillation but at 6 Hz rather than 1 Hz.
The manufacturer confirmed that this oscillation is not normal and wanted the unit back
for repair. A software problem might have been fixed in a few days. A hardware repair
however was estimated to be a month or more. The flight C-MIGITS is already in the
shop for repair and may be as much as a month away from being returned.
The possibility exists of obtaining an immediately available, new, C-MIGITS unit. The
cost is about $21,000.
After reviewing the various options discussed above, the decision was made to repair the
existing C-MIGITS. The problem turned out to be a broken coax antenna lead. Repair
and checkout are stated to require two weeks.
JRFEngineeringServicesX-37MonthlyReportOctober31,2000Page5
X-37
Program
Analysis of loads into X-37 from the B-52 is being conducted. The loads will then be
applied to the vehicle "Build To Packages" to determine if the designs are adequate. The
results of this may affect structures and other components. Since hardware is already
being fabricated and purchased, results could have significant impact. The problem is that
having hardware built tends to ratchet the weight up. If hardware is already built and
loads analysis shows that it can be lighter, it is unlikely that the part will be scrapped and
a new lighter one built. On the other hand, if the analysis shows that the part needs more
strength, something will probably be "scabbed on", almost certainly heavier than a part
optimumly designed for the loads in the first place.
Boeing is working both Shuttle and B-52 loads issues very hard and hope to come to
closure on this topic within a few weeks. They feel that their analysis is converging to a
solution. Dryden loads experts are working with their Boeing counterparts.
The acoustic environment on the pylon remains a major uncertainty. It seriously impacts
the engine and the entire aft end of the vehicle. DFRC has provided only very
rudimentary data to Boeing regarding acoustics. They claim to have no detailed model of
the acoustics. I find this astonishing considering the variety of vehicles that have flown
on this B-52 over some 40 years beginning with X-15. Numbers like 150 dB are bandied
about for antennas on the vehicle. This is huge amount of energy. It is 20 to 30 dB above
the spec for the SRAM missile, which flies on a nearly identical pylon position. A very
large number of thin-skinned aluminum vehicles have flown on that pylon (M2-F2, HL-
10, X-38, etc.) and I don't think they could have tolerated such an environment.
Something does not make sense and I find it hard to understand why DFRC is not able to
provide better information. (Bear in mind of course, that I am reporting the Boeing side
of the story.) In any case, Boeing has obtained X-38 acoustic data from JSC and is using
that for design. That should be conservative since X-38 is a bigger, wider vehicle and
parts of it will be much closer to the B-52 nacelle.
Generally speaking, it appears that the loads issues are being worked and that cooperation
between DFRC and Boeing is fairly good at the working level. Unfortunately, the
analysis is coming to closure later than would have been desired, resulting in possible
weight and/or redesign problems as noted above. The one exception is the acoustic
environment, which, for whatever reason, remains fuzzy. Other than keeping an eye on
the situation, I do not believe any specific action is required by the NASA P.O. although
helping to unravel the acoustic confusion would certainly be a benefit.
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JRF Engineering ServicesX-37 Monthly Report October 31, 2000Page 6
Vehicle Design
The vehicle weight is at about 6439 lb., about 60 lb. over target weight. The growth curve
continues to flatten out but still has not turned downward. Thus weight is still "holding",
i.e. climbing only slowly. However there is great concern that there are many unknowns
that may still cause a large increase. Fabricating hardware while still doing loads analysis
carries this risk with it.
Propulsion
Rocketdyne is having cash flow problems and may have difficulty continuing through the
end of CY2000. The tentative plan is to work only on the Qualification engine for the rest
of the year and put off work on the Flight engine until later. This would apparently solve
the cash flow problem now. The downside, predictably, is increased overall program cost
resulting from building engines sequentially rather than in parallel.
Rocketdyne is looking at the costs of doing vibration tests on the engine to support
Shuttle integration. They had not originally planned to do any such testing. This was
probably a case of excessive optimism.
The zero-g tests have been completed. There was some difficulty in getting the
information because of the NASA data recording approach. At this point it is not known
whether the propellant level sensors worked or not. XXXXX
The propulsion review with the Shuttle safety board generally went quite well. The
upshot is that the board feels that, with oxidizer system as designed, they are not unduly
concerned with the hydrogen peroxide. It turns out, however, to the surprise of many, that
they are more concerned about fuel. A little additional oxygen, even if hot, does not
worry them so long as there is no damaging plume impingement. A fuel spill however
could result in a serious fire. Boeing is looking at the issue.
Despite the concerns regarding the B-52 inputs to the engine, Rocketdyne is not currently
working on the analysis of this issue. They are not funded for this task and currently are
making a proposal to Seal Beach for funding to support the analysis.
Rocketdyne is considering two approaches to resolving the issue of the B-52 loads. On
option is to build up a test engine out of non-flight parts and subject it to vibration and
acoustic tests, which would envelope the expected flight environment. The other
approach is to build a more detailed computer model of the structure and attempt to
qualify it by analysis. It is not clear which option is the lowest cost. Rocketdyne is
running a cost analysis. Vibration facilities are available at low cost however it would be
necessary to build a test fixture and a second gimbal block and gimbal interface bracket.
The gimbal hardware is probably more expensive than the fixture.
Rocketdyne intends to have an agreed upon plan for the qualification issue by the end ofOctober.
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JRF Engineering Services
X-37 Monthly Report October 31,2000
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One positive aspect of the testing option is that it would qualify the gimbal block. As
noted previously, the original block had huge margins but Rocketdyne changed the
materials to reduce weight. Now_ no one is really sure what the margins are. Although
there are plenty of assurances that we have lots of margin, the case for testing the block is
much stronger than it would have been with the original.
Rocketdyne is working on the Action Items from the recent internal and external design
reviews. Naturally there is some overlap and repetition. Most of the items from the
internal review have been dealt with. They are working with Reggie Alexander on a
closure schedule for the items from the external review.
To address the concern over a possible fuel spill in the payload bay (see last week's
report), Rocketdyne is adding two additional relief valves so as to provide a double
inhibit between the fuel and the payload bay. This adds weight but appears to beunavoidable.
An additional complication with the gimbal block design used on the X-37 is that it is so
designed that the tightness of the assembly bolts defines the load on the gimbal joint. The
Shuttle lateral load environment may demand tightening up the bolts, conceivably to the
point that the actuators may have trouble moving the engine. In the original application of
the gimbal block, this was not a problem because it was always vertical and the engine
was firing at liftoff. Here, the engine is off and the loads are lateral as well as axial. It is
probable that the Shuttle nose gear slap-down loads are the driving case.
It turns out that there is another piece of hardware that must be fabricated: the oxidizer
pump inducer. One exists but another is needed. The question then arises, is it better to
make two so that what is tested in the qual engine is the same as flight. There is a
tendency to say "Why bother" if the new one is made of the same material, to the same
print. However, the answer was not that easy. The shape is a complex compound curve
defined by certain specific points. The fabrication technique is quite different with
modern machines. Thus while the defined points may be identical in both cases, the exact
shape between them might vary. There was concern that such subtle differences can have
impact upon performance, natural frequency, cavitation, etc. After due consideration,
however, Rocketdyne has opted to build just one. The current thinking is that the
differences would be too small to matter, especially given the low head rise of theinducer.
When considering testing of a structural test model engine to resolve the issue of the
ability to of the engine to withstand B-52 and Shuttle loads, the question arises as to the
test level. Clearly the test levels must envelope the worst case flight environment. The
question is, by how much margin. In spacecraft testing, a structural test unit and/or a qual
unit might be run at 6dB above expected flight while a flight unit might see 3 dB over.
The question is, do we want to go this high on a test article engine. Rocketdyne is
uncertain as to the answer. While the answer will depend to some degree upon further
analysis of loads and capability, I am against pushing to high levels. We have precious
JRF Engineering Services
X-37 Monthly Report October 31, 2000Page 8
little hardware. We need to qualify it but not to break it in an effort to hit arbitrarily
defined levels. This needs some discussion.
Flight Sciences
Calibration of the model RCS thrusters is complete at LaRC. The RCS model is back at
AEDC for installation. Testing should begin soon. CFD analysis is in progress to provide
a comparison with the test data.
The tunnel work at NASA Ames will probably be less fruitful than was hoped. They are
having difficulty hitting the planned Reynolds number points. Whether this results from
problems with the tunnel or inexperience of the operators is not clear.
Structure
Much of the concern regarding the loads on the ruddervators stems from the fact that
Boeing originally planned on deflecting the surfaces 5 degrees while on the B-52 as part
of the checkout procedure. They designed the load capability for 10 degrees deflection to
provide margin. Initially DFRC said this was okay. Now however, DFRC's position is
that they must deal with a full 40 degree deflection. At the originally planned airspeed of
300 keas the loads at full deflection were totally unacceptable. As a result airspeed was
reduced to 260 keas. Loads are acceptable at this speed with no gusts. However the
defined 37 ft/sec gust would fail the structure. The compromise is that, in the event of a
hardover failure, the B-52 will immediately slow to 230 keas, at which speed the loads
are tolerable even with the worst case gust. This compromise is based upon the fact that a
37 fi/sec gust is unlikely at best and is very unlikely during the brief period ofdeceleration.
Analysis is going on in this area. It may still be necessary to beef up the fuselage at the
points where the ruddervator loads are absorbed. As noted below, it is too late to do
anything about the sill longeron but other elements can be strengthened, if needed, to
accept the loads.
The door sill longeron tooling is complete. While this is good news in one sense, it means
that the longeron configuration is fixed and that no weight reduction can be had if loads
turn out to be lower than the design values.
The installation of the X-37 in the Shuttle is complex in terms of structural analysis. The
X-37 is supported on two pallets, each of which are independently attached to the Shuttle
payload interfaces. The aft structure of X-37 is bolted to a plate attached to the aft pallet.
The plate is parallel to the Shuttle aft bulkhead (horizontal in launch position). At the
front end, two trunnion pins on the X-37 rest in trunnion mounts on the forward pallet.
One can easily see that there are many degrees of freedom and that it is not determinant
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JRF Engineering ServicesX-37 Monthly Report October 3 I, 2000
Page 9
structure. Initial analysis tried to make do with a simple static model but this did not give
realistic results. This in turn forced use of a complex dynamic model to determine the
loads. The results of the more complex analysis may impact the design.
Substantial weight was saved in the Shuttle interface areas, both forward and aft, by some
fairly detailed analysis. This has helped stem the weight growth
Operations
The combined team is evaluating X-37 electrical requirements on the B-52 to determine
what if any changes will be required at the B-52 interface.
Range Safety reiterates that, under the current scheme, if the vehicle TM downlink is
lost. the vehicle will be terminated no matter how welt it was flying prior to the loss.
Initial antenna pattern testing on the X-37 configuration has been completed.
Several issues have come up regarding FTS batteries. In one case, Boeing wants to fly Li-
ion batteries because of weight and temperature range tolerance. However, such batteries
have not been used in this application previously and are not considered properly
qualified by Range Safety. Needless to say Range Safety is very conservative about new
hardware. Ni-Cd and Ag-Zn batteries are qualified and acceptable to the range but are too
heavy and lack the temperature tolerance that Boeing feels they need. In order to use Li-
ion batteries in this application, an extensive qualification program would be required.
The required operating lifetime of the batteries is driven by requirements to operate
through descent, entry and landing, i.e. from deorbit burn through wheel stop, plus all on-
orbit checkout. Range safety insists, reasonably enough, that the final on-orbit checkout
also be done on the actual FTS battery. In addition there are earlier checkouts. This could
translate to the FTS being on the battery for one to three orbits prior to the deorbit burn.
This becomes a significant number of watt-hours and drives battery size. A possibility is
to "diode or" the vehicle power into the FTS circuit so that preliminary checks could be
done on vehicle power before switching to the FTS battery for the final check. If there
will be some significant time between the final check and the deorbit burn, it may be
possible to switch back to vehicle power until just before the burn. Once the burn starts
however, the FTS battery is to be locked in as the only power source. This approach may
satisfy the range while cutting down FTS battery weight.
A B-52 interface meeting was held between Boeing and DFRC and seemed to go very
well. Most of the issues appear to be ironed out and Boeing feels ready to move forward
with the design effort.
The acoustic environment data on the B-52 that was originally presented to Boeing is
generally held to be high by an order of magnitude. This, if true, should greatly reduce
the concern about acoustically driven loads.
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JRF Engineering ServicesX-37 Monthly Report October 3 I, 2000Page 10
It appears that approval will be granted to use the Ensign Bickford laser firing units ofFTS.
DFRC is urging the use of a C-band beacon. They admit that such a beacon is not
mandatory but express the opinion that not having it substantially increases the risk to the
vehicle and the mission since, if TM is interrupted, Range Safety will destroy the vehicle
no matter how well it seems to be flying.
All B-52 interface work and analysis to date has been based upon the B-52B (the
currently used aircraft). When the planned B-52H conversion becomes available, it is
hoped that the change will be essentially transparent to the user. There are somedifferences however. The mount on the H sits farther forward than it does on the B. As a
result, there may be less separation down force when dropping from the H because the X-
37 will be more exposed to the upwash at the wing leading edge than it his when
mounted on the B. It is reported that the X-I 5, a longer vehicle that protruded farther
forward, experienced less downforce than stubbier vehicles.
The acoustic environment on the H should be much better, both because of the forward
location and the quieter turbofan engines.
A possible disadvantage of the H is that it apparently will not have the wing structural
enhancement that is incorporated in the B. This limits the weight of the drop vehicle. It is
not clear whether this will be a problem for X-37. When the H becomes available (target
January 2002), the B may be placed in flyable storage unless specific users are identified.
The B-52 is unable to accurately simulate the entry vehicle conditions at the drop
altitude. Paradoxically, it apparently cannot fly slowly enough at 40 to 45 Kft. altitude to
simulate the speed of the X-37. This is probably a manifestation of the very high drag of
the X-37. The B-52 must maintain 0.75 to 0.8 Mach at these altitudes. Current drop
condition will be 43,000 ft (about 40,000 agl) at 200 keas, which is about Mach 0.79
JRF ENGINEERING SERVICES4023 Shadow Run
Las Cruces, NM 88011
(505) 532-9572 (phone/fax)e-maih [email protected]
30 November 2000
To:
From:
Subject:
Edgar W. NicksJim French
X-37 Monthly Report-November
C: S. Turner, Lt. Col. Johannessen, M. Harris, J. London, B. Armstrong, S. Stewart, Maj.
Titus
X-40A
Flieht Test
Another rain on 29 October left standing water on the lakebed, precluding operations
early in the week. However, by Friday, 3 November, it was dry enough for additional taxi
testing. These final low speed taxi tests were generally very successful. The maximum
speed obtained was 42 mph. Some minor uplink problems were encountered but these are
generally considered to be caused by obstructions. High speed testing was scheduled to
begin the week of 5 November.
The Air Force Flight Test Center (AFFFC) approved the higher broadcast power for
Command and DGPS requested for the vehicle (see last month), however, they did not
approve the requested increase in bandwidth. The logic for this is not obvious since the
total bandwidth requested lies well within the allocation for DFRC. Boeing views this as
simply more obstructionism. DFRC seems unwilling to push on the FTC on this matter
and became very irate when Boeing personnel proposed to go directly to the FTC. The
political environment seems to get progressively worse.
Because of concern about the rain on the lakebed, discussions were initiated with Range
Safety and the AFFFC regarding landing on the hard surface runways. While the answer
was not the fiat "No" that I expected, a number of problems were raised, not the least of
which was schedule. Various USAF programs are having to work six or seven days per
week to get main runway time. Because of this X-40A will not be able to schedule the
runway ahead of time during the week. Scheduling ahead on weekends might be easier.
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JRF Engineering ServicesX-37 Monthly Report November, 2000Page 2
This really seems like a show-stopper. We could hardly sit around for days with the X-
40A loaded on the B-52 just in case somebody cancels. The possibility of using lakebed
Rwy 22 was also broached. This might be possible if 25 were unusable. If 25 can be used,
22 will probably not be approved. In order to enhance probability of flight, we need to be
able to land on any runway and to fly on short notice. The practicality of this is TBD. It
has been concluded that using the Main Base runway (paved) has an acceptable Ec on
weekends however such use has yet to be approved at the top levels.
Some of the lakebed runway is still soft and has sinkholes caused by the rain. Work is in
progress on the runways. More length is needed for the high speed work.
Boeing wants to get two flights in before the end of the CY. The schedule to do this is
very tight already. The helicopter and crew are at EAFB. A number of tests are required
before flight and, of course, Mother Nature needs to cooperate by providing dry weather.
The helicopter crew is under orders to head for home no later than 21 December.
Investigation of the anomaly that involved blowing the parachute piston out of the
vehicle indicates that excess flow through the DFRC-mandated second solenoid was the
problem. For off-vehicle testing, flow was reduced by plugging one of the three orifices.
Testing was done with both solenoids and 3000 psi supply pressure and one solenoid at
1800 psi. Both were successful.
After permanent modifications are made, three more tests will be conducted on the
vehicle to verify the modifications. However, at month's end, these tests have not yet
been conducted. The possibility of letting the sabot depart the vehicle is being
considered. Boeing wants to fix the problem but apparently there is some dissension
surrounding the issue.
Vehicle Systems
After some delays caused by hardware problems, validation of the build 7.1 software
began on 10/31.
The capacitator for the regenerative power protection modification has been received and
installed.
Following the parachute tests noted above, the orifices will be modified to give
equivalent flow, with all three open, to that obtained in the tests with one plugged.
G,NI&C
The C-MIGITS was brought up from Anaheim late on 10/31
/4
JRF Engineering ServicesX-37 Monthly Report November, 2000Page 3
X-37
Program
The forthcoming discussions of program modifications will be interesting. I think that
there might be ways to obtain much of the desired data without building a second
airframe or risking our only X-37 airframe. Basically this involves use of the X-40A as
the atmospheric test vehicle and dropping it from the Scaled Composite Proteus aircraft.
Proteus was investigated early in the program but rejected because it could not carry X-
37 without significant modifications. It could, however, carry X-40A. In fact it could
launch higher and faster than the B-52. Scaled had no particular issue with dropping a
single-string controlled vehicle. The X-40A carries the CADS so testing with it would
give experience with that system. The planform and aerodynamics of the X-40A are
somewhat different from X-37 with the latest changes to the latter but since an extensive
wind-tunnel data base exists for both vehicles, correlation of results should not be
difficult. I believe that this option is worth considering as compared to building a second
X-37 air frame.
It seems likely that very little will be done before the week of 4 December because of
activity on the NRA 8-30 proposal. To meet the due date, that proposal will have to be
through the writing stage by the end of that week. Activity on the X-37 should pick up at
that point.
I have done some preliminary looking into their requirements and compliance matrix, via
telephone. The summary is that, in the beginning, they never really had such a thing.
There was pressure from within and without Boeing that they really needed some
formalism in this area. As a result, they are now working on back-filling this particular
lack. I have an appointment to go over all this with ray Bartlett during my visit 6 and 7
December.
Vehicle Design
The vehicle weight is still slightly above 6400 lb. This number includes the 500 lb
payload weight. The lower limit of the zone in which the vehicle will have to be
placarded for sink rate and possibly other parameters begins at 6400 lb and extends to the
maximum weight of 6800 lb.
The current weight is probably tolerable but there are several potential increases looming
that considerably exceed any anticipated reductions. Thus the weight is almost certain to
increase by a significant amount.
/3-
JRF Engineering ServicesX-37 Monthly Report November, 2000
Page 4
Some of the weight growth comes about from actual data being received on the actuators.
They are heavier than planned. This is aggravated by the decision to have actuator
commonality to save cost. This means that some actuators are heavier than an optimum
design would be. Because most actuators are aft, ballast is necessary to control CM,
further aggravating the weight situation. Another source of weight growth is the problem
with the lower fuselage skins described later.
The acoustic loads still appear to be too severe even using the X-38 data. The solution to
this issue is not clear.
A question has arisen over whether the X-37 needs to be Fail Operational / Fail
Operational / Fail Operational / Fail Safe or just Fail Operational / Fail Operational / Fail
Safe. The consensus seems to be that it is the latter requirement that is appropriate for this
vehicle.
Propulsion
Rocketdyne is fabricating hardware and preparing to assemble the Qualification engine.
Money is tight but Rocketdyne management feels that they can meet the schedule.
Most other activity is on hold while decisions are awaited on various proposals, e.g. the
Brassboard. Most Seal Beach personnel are working on the NRA8-31 proposal.
Flight Sciences
The wind tunnel work is going very well for the most part and is nearing completion.
Low speed testing is essentially done as is much of the medium speed work.
In the high-speed regime, the first set of Mach 10 data were obtained when the heaters
failed in the tunnel. Repair is expected to take considerable time, therefore the model is
being removed and mounted in the Mach 6 facility.
With the completion of medium speed tests at AEDC, that model is headed for Ames
Research Center. Tests will begin there in January.
The RCS tests in Tunnel A and Tunnel B are done and work In Tunnel C will begin
shortly. Preliminary looks at the data are very promising and seem to correlate well with
the CFD. There is no indication of serious coupling problems such as plagued X-33.
If all continues to go well, all but two sets of wind tunnel work will be complete by the
end of December. Because the engineers are wrapped up in the testing, there has been
very little analysis of the data but quick look analysis looks good.
/6
JRF Engineering ServicesX-37 Monthly Report November, 2000Page 5
The Hight Sciences lead will be pressing to add a small set of tests at high altitude, say
270,000 ft. there has been little attention paid to that regime and it would be good to have
some data to anchor CFD.
Structure
A serious problem has arisen in fabrication of the lower fuselage skin. When the skin was
pulled from the mold, it was noted that, because of core condensation at the lower
corners, the vertical walls leaned inboard. Springing these vertical walls out to the proper
position overstressed the skin in the comers. Two fixes are identified. Both involve
cutting out the core and inner skin in the comers. In one case, the remaining core would
be panned down and several layers of cloth added to make the comers into a single thick
skin section rather than a honeycomb structure. In the other case, separate parallel rows
of honeycomb, probably three, would be laid in the cutout and new skin added on theinside. The former fix is favored.
Also a triangular area high on the port side just forward of the wing cutout experienced
core collapse. The offending core and inner skin will be cut out and replaced.
There will be a weight penalty of perhaps 15 lb for these repairs. The irony is that, if
heavier core had been used, the condensation and collapse probably would not have
occurred. Heavier core was planned originally but was replaced with lighter material to
save weight. This repair probably more than eats up the original gain. This is not
particularly a matter for recrimination. The program is pushing as hard as it can to reduce
weight. It is to be expected that, once in a while, they will overshoot.
It will be necessary to beef up the fuselage structure that takes the ruddervator loads in
order to meet DFRC's requirements for a 1.25 factor of safety on a hardover surface at
260 keas. More weight.
The change request to beef up the ruddervator attach structure has been submitted but has
not been approved. These changes are required to withstand loads caused by hardoverdeflection on the B-52
Operations
DFRC has not backed off on the very high B-52 acoustic inputs originally given to
Boeing. Boeing is continuing to work using X-38 data. There may be some risk that thiswill become an issue later.
Boeing has been planning to test each conlrol surface actuator individually just before
drop and then to leave the actuator powered but commanded to neutral position while
/7
JRF Engineering ServicesX-37 Monthly Report November, 2000Page 6
others are tested. When all are tested, X-37 will be ready to drop. DFRC is saying that
each actuator should be tested individually and then turned off. The X-37 would be
dropped with actuators unpowered. They would be powered up a few seconds after
release.
This seems ridiculous. Turning the actuators off partially invalidates the checkout just
completed. Further, as discussed in earlier reports, it may not be safe for X-37 to dropwithout controls active because of the effects of B-52 airflow.
The procedures and documentation for the Shuttle interface will require major manpower.
Boeing may not be able to do it alone. They may require help.
NASA MSFC and DFRC are cooperating on a paper that will strongly recommend
inclusion of a C-band beacon in X-37. Boeing feels that it is unnecessary because the
worst case situation shows VAFB picking up telemetry a safe distance off-shore.
However, the safety people are strongly in favor of including the beacon.
The requirement for a 72-hour on-orbit checkout prior to re-entry still stands but a great
deal of clarification is needed.
I have reviewed the first draft of the KSC Ground Operations Plan and provided
comments to Boeing.
/8
JRF ENGINEERING SERVICES
4023 Shadow Run
Las Cruces, NM 88011
(505) 532-9572 (phone/fax)
e-mail: [email protected]
30 December 2000
To:
From:
Subject:
Edgar W. NicksJim French
X-37 Monthly Report - 30 December 2000
C: S. Turner, Lt. Col. Johannessen, M. Harris, J. London, B. Armstrong, S. Stewart, Maj.Titus
X-40A
Flight Test
Taxi tests have reached 60 mph. Some anomalies have occurred with C-MIGITS and
RAJPO involving resets of the microtracker during the taxi tests. This is being
investigated and is tentatively attributed to battery problems in the device.
The first captive flight test was scheduled for 8 December pending approval by the
MSFC Center Director. The approval was received and the test was successfully
conducted as scheduled. Several runs were made including climbs and descents to
calibrate the radar altimeter. The only serious problem noted to date was dropouts in the
C-MIGITS data. It is not known if the problem is with C-MIGITS or with the ground
station. In either event, it is potentially a major problem since loss of data during free-
flight could result in Range Safety aborting the mission.
Except for the C-MIGITS problem, the captive flight went very well, validating
procedures and giving the crews valuable experience. Some adjustments in the sling will
be required to get the proper angle on the X-40A but that should be minor.
The helicopter crew is being sent home for the holidays. The C-MIGITS data dropouts
experienced on the captive flight must be corrected prior to further flights. So far, no
clear explanation has emerged and it seemed foolish to keep the crew sitting around when
the probability of another flight before the Christmas shutdown was becoming
/Y
JRF Engineering ServicesX-37 Monthly Report 30 December, 2000Page 2
increasingly remote. Therefore, the earliest possible date for the next captive flight will
be early January.
Work continued, during the month, on repair of lakebed runway 25.
It was reported earlier that the test team was investigating an anomaly that involved
blowing the parachute sabot out of the vehicle, apparently because of excess flow through
the DFRC-mandated second solenoid. It was reported to me and hence in these reports
that, in off-vehicle testing of a configuration where flow was reduced by plugging one of
the three orifices, two tests, done with both solenoids and 3000 psi supply pressure and
one solenoid at 1800 psi. were successful. It turns out that they were successful in the
sense that the FTS worked and the parachute came out. However, the sabot ejected as
well.
Evidently, the problem is that, when the 'chute ejected, the sabot was stopped by its
restraint cable as planned. However, over the next second or so the pressure behind the
drive piston, continuing to build up, blows the sabot out. By this time the 'chute is
probably fully deployed and the sabot may punch a hole in it.
The easiest solution seemed to be to eliminate the sabot restraint cable so that the sabot
exits the X-37 with the 'chute and will fall away before the 'chute fills. However there
was also a push, apparently mostly from Boeing, to "Fix it right" so the system operates
as originally designed. The system was finally modified so that the sabot was restrained;
see Vehicle Systems below.
The good news is that the FTS works fine and the 'chute has never failed to eject
properly.
Vehicle Systems
The parachute canister back plate was routed out to make room for the larger snubber
required to hold the sabot in the vehicle. The machining made a portion of the plate too
thin so that a strengthening plate was bolted to the back plate to strengthen it. This plate
interfered with structure around the canister requiring further modifications. However,
the system was ultimately tested and appeared to be fully successful. This should clear
one obstacle from the path of free flight.
The C-MIGITS dropout problem is being closely investigated. It is not yet clear if it is a
C-MIGITS problem or a communications issue.
_0
JRF Engineering ServicesX-37 Monthly Report 30 December, 2000Page 3
X-37
Program
Boeing is working to develop a system that shows requirements and their derivation as
well as the approach to compliance. The system was briefed to the NASA Program
Manager on 6 December. The approach seems promising but rather elaborate. It will be
interesting to see how well it works in practice. As noted earlier, the Boeing project really
had no system for keeping track of these things until this task began recently.
Vehicle Design
As predicted in earlier reports, the weight increased by about 190 lbs. to 6621. This is
only 179 lbs. below the limit. Possible increases are identified as 158 to 203 lbs. and
possible decreases now are about 152 lbs. These numbers change daily.
The latest increase came from a number of sources. The actual actuator weights are 94
lbs above the estimates. The lower fuselage skin repair is coming in at about 27 lbs. An
increase in battery capacity from 30 to 43 watts-hour will cost about 30 lbs. The
remainder of the increase is from a variety of small items.
The above does not include the cabling issue discussed below.
There is some possible relief from the actuator weights. Moog makes several different
motor sizes, gear box sizes and jack screw sizes, which they can mix and match rather
easily. At the moment, all actuators are the same with size driven by the largest
requirement. Given the variety of hardware available, it is not clear that cost of
customizing the actuators for each application would be prohibitive. The numbers of
items are not so big that there is any great advantage in quantity buying of all one size (at
last in the opinion of some Boeing personnel). Also, all actuators have dual motor coils.
This may not be required in every case, affording further opportunity for reduction.
Propulsion
The NASA Propulsion FDR team has expressed concern regarding the small amount of
hard data in the Propulsion Splinter package. I still do not have EVS access however, I
reviewed the document while I was at Boeing this week. RIDs and comments were
submitted to the Propulsion FDR leader. My comments follow:
2/
JRF Engineering ServicesX-37 Monthly Report 30 December, 2000Page 4
• As suggested in verbal discussions, the package was somewhat disappointing in
the lack of quantitative data. The package is a good status report but without
much supportive detail.
I find no major fault with the fuel tank except that the fabrication procedure is
very labor intensive. It probably does not matter greatly for making a single unit,
but it certainly does not take advantage of the producability of compositestructures.
Details on fabrication of the oxidizer tank are scarce. I infer that it is made in two
halves and girth welded. There is little information about the material
characteristics, loads, weld verification, etc.
On page 20 under "Propellant Management" there is mention of a "bubble
position wicking vanes". Wicking implies a large surface area. If this is true, it
will tend to promote decomposition of hydrogen peroxide.
There is some inconsistency in the propellant dump procedures. No pressure
level is specified for Depletion Dump Concept #1. Whereas, pressure settings P-5
and P-6 are quoted for Depletion Dump Concept #2.
• In Depletion Dump Concept #1, is the pressure pulsing process controlled by the
flight computer?
I have some concern about the emergency deorbit and propellant transfer process.
The timelines are tight and it is not clear as to how the procedures are loaded into
the vehicle and when and how the process is initiated.
This concludes the splinter comments.
After having been reasonable and cooperative up to now, the Shuttle Safety Board has
recently become very inflexible about hydrogen peroxide. This appears to be a direct
function of the increased visibility that the project "enjoys" at JSC. Frank Benz, formerly
of WSTF and now at JSC has a firm opinion that peroxide is unsafe and that there is a
lack of sufficient data to prove it otherwise.
This position is not supported by fact. There are huge volumes of data generated in the
1960's. While there was some difficulty in corroborating those data with recent tests, the
discrepancy was traced to differences in test techniques with the modem methods being
unsuitable to peroxide. The latest results from material tests at FMC look very good and
agree very well with the old data. In short, there seems little or no reason for concern.
However, these emotional prejudices may be hard to overcome.
The material choice for the RCS tank is being revisited. Aluminum alloy 6061 is only
slightly inferior to 5254 in temps of peroxide compatibility and, being significantly
stronger can potentially save significant weight.
dd
JRF Engineering ServicesX-37 Monthly Report 30 December. 2000Page 5
A recently expressed concern is that of decomposition caused by adiabatic heating when
the liquid is introduced into an evacuated line. Hydrazine is prone to this problem, which
caused an explosion in a communications satellite (one incident out of many hundreds of
times that this has been done.) Data on peroxide indicate that it is not prone to this
problem so it is probably not a real concern.
A question was raised regarding a 9-valve relief valve array being discussed for the X-37
propellant tanks in the Shuttle. This arises from a literal interpretation of two
requirements: 1) three inhibits against inadvertent venting of fluids into the payload bay
and 2) three inhibits against over-pressurizing the tanks. Blindly following this logicleads to three valves in a row in one line but with a branch at each valve in case that valve
jams. To meet the requirement, each branch then must have three relief valves in it. This
leads to a nine-valve array. No one thinks that this is viable because of weight, cost, and
complexity. Boeing and MSFC propulsion personnel are working to develop a concept
using fewer valves and incorporating some burst disks.
Launch Vehicle
Since the X-37 is now a primary payload and must bear the full brunt of Shuttle costs,
other launch options are again of interest. I have been discussing this with cognizant
Boeing personnel. It appears that most of the required information is available from the
studies done about a year ago before the decision was made to go to Shuttle. I have
advised Boeing to gather the data previously done, update it as seems suitable based upon
advancement in the design process, and put together a summary that will help in
comparison of the options. I suggested that, if they have a recommendation, they shouldmake it.
A briefing was presented to the NASA program office on 6 December summarizing
Boeing's approach. Boeing feels that the Delta IV M+ with a 5 meter fairing and two
solid strap-ons is the proper choice for an ELV.
In the initial cost evaluation however, the cost of the Shuttle launch comes in at around
$81M to $86M while the ELV is about $117M. The primary difference is the $67M
direct price for the Shuttle versus around $93M for the Delta IV. This does not, of
course, include the hidden cost of Shuttle; the numerous reviews and extra analyses
required. This can only be made worse by the recent increase in hostility toward
peroxide. An additional consideration is that no version of Delta IV has yet flown.
Flight Sciences
The wind tunnel testing continues essentially on schedule. The RCS model is about to
enter the C tunnel at LaRC for test in the Mach 10 regime. The lower speed tests are
complete and the preliminary results look very good. Correlation with CFD is also very
23
JRF Engineering ServicesX-37 Monthly Report 30 December. 2000Page 6
good. Some minor problems are delaying tunnel entry, but this should not substantially
impact the completion date.
Avionics
The current cabling weight is 476 lbs for 150 or perhaps over 200 cable sets (there is
some uncertainty). However, the total expected number of cable sets is 370. The
potential for a substantial weight increase is significant. This results from poor
estimating. Personnel simply left out a large number of cables in their original numbers.
The SIGI power supply for GPS/INS is qualified to aircraft specifications.
Requalification is required from compliance with the common specification. Changes to
the hardware will probably be required. This will cost some hundreds of thousands of
dollars. One wonders why this seems to be coming up as a surprise this far into the
program.
G., N., and C
Because the hinge moments were severely underestimated, flaperon deflection is being
limited to 8 or 9 degrees as the vehicle slows toward the transonic regime. This is not a
popular idea with controls personnel who want all the control authority they can get
during this critical phase. In the absence of any serious disturbance (e.g., a strong gust)
the limited deflection is probably acceptable but a major disturbance could be trouble.
The G, N, &C staff is carefully evaluating the requirements for control deflection during
the low supersonic and transonic speed regimes. The loads developed from this analysis
will then be fed back to the actuator and structures personnel to ascertain what changes
may be required to meet the control requirements. This may have some weight impact but
the vehicle cannot be undercontrolled in a critical flight regime. It is almost certain that
the full deflection of 40 degrees will not be required, thus the hinge moments and
resulting loads may not be as severe as once thought. However the vehicle will certainly
require more control authority than can be afforded by the 9 degree (or thereabouts) limit
that the current structure and actuator capability imposes, Boeing management is taking
the position that there is no significant problem but anything that may cause more weight
growth is at least undesirable at this point.
Structure
The collapsed core on the lower fuselage panel has been cut out in preparation for
replacement. The cutout of the core in the lower fuselage comers was last reported in the
layout process preparatory to beginning the repair.
24-
JRF Engineering ServicesX-37 Monthly Report 30 December, 2000
Page 7
Operations
The C-band beacon continues to be an issue. DFRC is hard over that they want it.
Apparently the genesis of this demand is that on one Shuttle mission some years ago, all
the radars locked up on a 747 rather than the Shuttle for some period. So now theydemand a beacon with an identifier.
The practical fact appears to be that telemetry can lock on as the vehicle comes over the
horizon and should be satisfactory. However, any interruption in TM could be an excuse
to destroy the vehicle. The it will be a "We told your so" situation. The C-MIGITS
dropouts are probably adding fuel to the fire even though the systems involved are
entirely different.
d5
JRF ENGINEERING SERVICES4023 Shadow Run
Las Cruces, NM 88011
(505) 532-9572 (phone/fax)e-maih [email protected]
To:
From:
Subject:
13 January 2001
Edgar W. NicksJim French
X-37 Weekly Report- 13 January 2001
C: S. Turner, Lt. Col. Johannessen, M. Harris, B. Armstrong, S. Stewart, Maj. Titus
X-40A
Work continues to resolve the C-MIGITS problem. Taxi tests are now planned for 17
January, the next captive carry for 24 January and a drop early in February. Boeing's
budget for this activity officially runs out at the end of February although they could
probably extend the effort through March. The push will be in the direction of finishing
by the end of February if possible. The helicopter crew is lost after 1 April.
Extensive data recording on C-MIGITS indicates that the microtracker resets occur when
the computer receives a long message from the dGPS. Partial messages are rejected but
cause no problem. Even if this is indeed the problem, what to do about it, in terms of
changing the system, is not clear. Boeing has analyzed the problem and feels that they
could safely turn off the dGPS just before drop. The inertial system is sufficiently stable
that it could carry out the flight to the runway without further dGPS updates. If this
concept holds up, this is probably the best solution. Given the short duration of the flight,
it seems unlikely that the INS would drift far enough the cause a problem. There is a
concern that the drop transient might cause a reset or some other problem. This needs to
be resolved because it is highly undesirable whether the dGPS is on or not.
Just to add to the headaches, there has been about 1.5 inches of rain. The dry lakebed is
now the wet lakebed. Even with no more rain, the lakebed runways are expected to be
closed into February. If there is more rain, the only hope of timely completion of the
program may be to use the hard surface runways if Safety will allow it. Boeing wants a
first flight on 5 February. That would make the hard surface runway (Rwy 22) essential.
Briefings to the Base Commander on this issue are in progress.
2_
JRF Engineering ServicesX-37 Weekly Report 13 January, 2001Page 2
X-37
Vehicle Design
The weight problem discussed previously is, of course, a concern to Boeing. After the
major jump that occurred in November/December, they have begun intensively working
the problem. Apparently there are several, not specified, weight reduction approaches
being considered. They are also looking at increasing the weight capability of the vehicle.
The limitations on weight are 1) planform loading and the resultant heating during entry,
and 2) landing gear capability. Probably there are others coming into play as weight
increases. The Chief Engineer expresses confidence that with the combination of
increased capability and reduced weight, Boeing can come to Rollout with acceptable
weight margin. This, of course, remains to be seen.
Propulsion
In an earlier report, it was mentioned that use of 6061 aluminum instead of 5254 was
being considered. That has been dropped for the main tank but is still being studied for
the RCS tank. The final result of this study is expected by the end of January. The weight
saving from using the stronger material may be significant.
27
JRF ENGINEERING SERVICES4023 Shadow Run
Las Cruces, NM 88011
(505) 532-9572 (phone/fax)e-maih [email protected]
24 February 2001
To:
From:
Subject:
Edgar W. NicksJim French
X-37 Monthly Report - February, 2001
C: S. Turner, Lt. Col. Johannessen, M. Harris, J. Sisk, A. Nolen, T. Taylor, S. Stewart,
Maj. Titus
X-40A
A captive flight was conducted on the morning of 31 January. It was successful other
than minor anomalies. An anomaly recognized prior to the flight was lack of continuity in
the drop signal cable. While this would have precluded an emergency jettison of the
vehicle, the helicopter crew felt that the risk was minimal and elected to proceed. The
cable had checked out correctly the day before so the reason for the problem is not clear.
One more successful captive flight was required before a free flight.
Two remaining issues required resolution prior to a free flight. The Divide by Zero issue
has not yet been put to bed. There was also the concern with C-MIGITS occasionally
losing satellites during simulator test must be dealt with. The Divide by Zero issue was
concluded to be no problem and the C-MIGITS issue a simulation problem.
Approval for testing was finally received from both the EAFC Base Commander and the
MSFC Center Director during the second week of February. The Base Command
approved use of the hard surface runway flight at any time but expressed a preference for
weekends, at least for the first one.
The next captive flight was scheduled to go off on Saturday the 10 th . This would have
allowed a free flight on Tuesday the 13 th. Weather prevented this flight.
Monday and Wednesday of the week of the 12 m were backups for the captive flight but
battery charge time and the need to have the runway free for the Shuttle preclude a free
flight after a Monday / Wednesday captive. Because of pilot/crew availability, runway
28
JRF Engineering ServicesX-37 Monthly Report February 2001Page 2
work, Shuttle. and holidays, the only dates left in February for flight operations were 20
through 22 and possibly, the 24 _h.
After many, delays, the next captive flight lifted offat 0700 hrs. on 14 February. Liftoff
was clean and smooth. Generally, speaking the flight went _ell until, at about 9.6 ft.
altitude on final descent, an event occurred with the on-board Flight Computer. The
computer stopped and could not be started on the ground until the computer was
rebooted. It was first reported that. had this event happened on a free flight, the vehicle
v,ould most likely have landed perfectly. It was believed that the computer was running
satisfactorily, just not communicating. It turned out however, that the computer had
indeed frozen. While there was some thought that X-40A might have landed successfully
from that altitude even without the computer, it is very unlikely. The vehicle issufficiently unstable that there is little chance that it would settle on to the runway on its
ox_n without further control. Even if it did. the probability' that it x_ould roll out
successfully without steering is small.
This Flight Computer problem is being investigated but no clear cause has been I\mnd as
of this report. They have been unable to duplicate the problem. They can cause resets but
not a lockup. Some consideration is being given to thermal-vacuum chamber runs with
the FC but the most logical answer appears to be to repeat the captive flight. A free flight
will be not permitted until this nev, anomaly is resolved: this means the captive flight will
have to be repeated.
Had the "'event" turned out not to be a problem, the first free flight could have occurred in
the 20-22 February time frame and the second 2-3 March. Assuming a decision having
been made that a repeat of the captive flight was needed, it was decided to try' for 24
February,. Unfortunately this did not allow sufficient time to get the helicopter crew back
from Alabama. The repeat captive flight is now scheduled for 2 March with 3 r_ and 4 'h for
backup. In the interim, crane tests will be performed to simulate the final few feet of
descent. This is scheduled for the 26 th. A thermal vacuum test for the FC will take place
on Tuesday
There is some thought that the helicopter may have to return to Ft. Rucker lbr
maintenance. If this happens, it will seriously impact cost and schedule. The Shuttle is
scheduled for a 5 March launch. This may impact runwav availability.
A lakebed landing is no longer an option for a free flight. Heavy rains in mid-month
have essentially filled it with water. The lakebed runways may not be available until
Mav or June. It is fortunate that approval finally came through for the hard surfacerunway.
Dale Shell has raised the issue of whether it is worthwhile to do a freeflight, if we have a
major failure and lose the vehicle, that will put a very bad light on the program. It is
getting late enough that any flight data will have little impact. Given the cost and
2Y
JRF Engineering ServicesX-37 Monthly Report Februar3 2001Page 3
personnel use problems caused by X-40A, it max, be that this question is v, orth thinking
through.
X-37
Program
Boeing is working out a new schedule aimed at dealing with the major funding shortage
during the current year.
Several weeks ago. I raised the somewhat heretical idea that perhaps the B-52 flight did
not provide enough information to be worth the cost and trouble. I have been
investigating the question with some Boeing personnel. The answers so far have tended
to support my original premise although not completely. The areas in which
aerodynamic trouble might be expected are the transonic regime, Mach 0.9 to 1.2. and at
touchdov, n. The B-52 flights get close to the lower end of the transonic regime but do
not reach the real conditions of interest. The B-52 drops do provide information on flare
and touchdown but those data could be obtained on a helicopter drop test (like X-40A). a
much cheaper and simpler operation that v,ould not impact vehicle structure as the B-52
loads do. The greater altitude, longer flight time and higher speed of the B-52 tests allow
the X-37 to fly' the Heading Alignment Circle (HAC). The people most interested in this
are not the aerodynamicists but rather the G,N.&C sensor people. I suspect that their
concern arises from worry about whether the GPS can retain lock as the vehicle comes
around the HAC at a steep bank angle. Clearly this is a crucial issue and must be
ansv, ered. One might question whether the B-52 test is the only way answer it. An
aircraft test of the guidance system might answer it just as well. The results of the B-52
flights are clearly desirable but are they worth the impact on the program? 1 believe that
there is enough doubt as to the answer to that question to make further investigation
worthwhile. I recommend that eliminating of the B-52 flights in favor of alternate
approaches be evaluated.
Weight
On paper, the vehicle weight has not increased greatly since the last report. That is, to a
degree, an artifact of the holidays when not much work was done. The current weight
estimate shows 6636 lbs., about 160 lbs. below the limit that can be achieved with
placards on vehicle operation. The currently catalogued potential weight increases and
decreases are about equal. However, this does not include the impact of the cable weight
underestimate reported previously. That is carried as a TBD. The estimate of this weight
increase is expected to be available this week and it is expected to be large. Effort is
being made to minimize the impact but only so much can be done. Going to fiberoptics
20
JRF Engineering Ser','icesX-37 Monthly Report February, 2001Page 4
has been suggested and would save a great deal of v_eight but it is a bit late for changes of
that magnitude.
A Weights Tiger Team is looking at ways to reduce weight but it is a difficult
proposition.
Propulsion
An X-37 Propulsion TIM was held at MSFC the week of 5 February. The purpose of this
meeting was twofold: to exchange technical data and to try to smooth out the very rocky
relationship between MSFC propulsion and Boeing Seal Beach propulsion personnel.
In general, I would characterize the meeting as successful and worthwhile. The technical
interchange was good. Perhaps more significantly there was considerable discussion of
the relationship between the organizations and the persons most involved in the friction
were face-to-face. It appeared that these persons were making a concentrated eflbrt to get
along. That attitude, along with better communications will solve the problem.
It became clear that much of the problem lies in failure of communication and
coordination. In particular, the unfortunate events at the last PSRP meeting, x_hile
exacerbated by' the personalities involved, could probably have been avoided entirely by
better pre-meeting coordination. Weekly telecons and monthly face-to-face meetings
should greatly improve the situation. There will probably be complaints about the time
involved, given the limited staff, but, nevertheless, I feel that it is worthwhile.
The discussions of the Brassboard test article clearly indicate the importance of that item.
This is especially true since the Brassboard activity is defined as including a number of
smaller preliminary tests. These latter would include, among other things, tests of
representative line sections filled with peroxide and held in vertical or horizontal attitudes
to investigate peroxide decomposition in an environment more typical of an operational
situation. This sort of information is vital for actual systems design and safety-relatedanalvsis.
One issue that was raised involves the possibility of eliminating the AR2-3 main engine
in favor of additional, perhaps larger, hydrogen peroxide axial thrusters. Boeing claims
that this will save 300 to 500 lb. dry weight and several million dollars. Delta V
capability would be about 1200 fl/sec maximum. These numbers may be somewhat
biased by' Boeing project management's desire to eliminate MPS.
Although it can be correctly stated that most of the X-37 technology demonstrations, on
the two planned flights, can be achieved with monopropellant system (the exception
being the one dealing with propulsion technology), there are other arguments for
retaining the AR2-3. One such argument is the perception that the program is further
31
JRF Engineering Ser_,icesX-37 Monthly Report February 2001Page 5
reducing its capabilities. This could be damaging in the eves of Center management and
Hq.
Additionally, eliminating the engine will reduce traceability to future Air Force
applications. It may be argued that this isn't a major issue since USAF interest appears
limited. This may change in the new administration, particularly if an officer like BG
Worden moves into a critical position.
Finally. removal of the engine means the X-37 is absolutely locked in to the Shuttle or
Delta IV Heavy for launch. Retention of significant delta V capability may open the door
to use of Atlas V or Delta IV Medium (assuming adequate fairing diameter).
The Tiger team on hydrogen peroxide compatibility seems a good thing and seems to be
v, ell run. The issues the,,.' propose to address are valid. The investigation of adiabatic
compression detonation (ADC) that the,,' propose is w'orth doing. There is some lore that
says it isn't a problem at 90% concentration but it would be nice to have that shown. This
work fits nicely into the propulsion technology line item. Programs such as SM\" that
require more advanced propulsion will want to investigate higher concentrations, e.g.
98_. These tests and the procedures and facilities developed for them can lead smoothly
into investigations of the (ADC) characteristics of higher concentration peroxide.
The majority of my activity the week of 12 February concerned the propulsion system.
most particularly following up on the TIM held at MSFC during the week of 5 February.
I have reviewed the materials test plan created by the Tiger Team. It is very thorough.
Upon conclusion, it will contribute significantly to the database for hydrogen peroxide
propulsion systems. All the A-series tests, while focused upon X-37 materials, are basic
materials characterization tests and have broad applicability. Of more direct support toX-37 are the C, D, and E tests./The one B test is not a test at all but more of an
evaluation and screening activity). The C & D series tests are tests of actual X-37 type
components in peroxide. These clearly have direct applicability to X-37. The E-series
refers to tests on the Brassboard propulsion test article, also clearly of direct applicability.
The details of some of these tests, particularly the Brassboard, are vet to be defined. This
definition process will bear watching to make sure that the greatest benefit is derived.
It might be argued that the A-series tests could be eliminated in part or in total in favor of
the results of the C. D. and E tests. 1 believe that this is true. However. given that we are
dealing with Shuttle safety. I fear that the probability of eliminating any of the tests is
very lov,.
The screening tests for Adiabatic Compression Detonation is probably worth doing just to
define whether we have the problem. The recent event at Stennis (even though it
occurred with a 98% peroxide) will have that concern foremost in many minds.
3,7
JRF Engineering Se_,ice.,,
X-37 Monthb Report Februa D 2001Page 6
Rocketdyne reports that they have been ordered to slov, dov,n to a \err low level of
operation. Much of the fabrication and assembly v,ork is being stopped and people
relocated. The slow down is being blamed on lack of a decision regarding cancellation or
retention of the MPS. If the program is slow:ed enough, the detrimental effect max' be as
bad as shutting down the program for a ),ear as was previously discussed.
The RCS system is generally going well. The only significant problem in the past fev,
weeks v,'as the discovery that a required change to the thruster valves had not been made.
Last year it was discovered that entry heat soak heated the valve coils to about 150F. This
adversely affected valve response. The valves were specified at 20 msec responses at
70F. The increased resistance at the higher temperature slowed the valves to an
unacceptable degree. The manufacturer was directed to correct this v,ith larger coils but
somehow the contractual v,ord never got through. This was recently discovered and is
nov, being corrected. Because of the slowed schedule, this should not be an issue.
The trade betv, een 5254 and 6061 aluminum for the RCS tank continues. In
compatibility tests, 6061 is v,orse than 5254 but. on the other hand. it is better than the
bladder material so there seems little reason not to go to the higher strength alloy and
save 5 or 6 pounds.
Structure
Work continues on repair of the lower fuselage. The honeycomb has been cut away and
the team is looking at number and orientation of plies to give the right strength and
stiffness. Repair of this fuselage section is the longest pole in the technical schedule right
now but, given the probable schedule stretch out due to funding problems, the repair v,ill
probably not be an issue.
Analysis of loads in the repaired area is being conducted to ascertain x_hether additional
structural members v,iil be required.
Flight Sciences
This area continues to be one of the most successful on the program.
Wind tunnel testing at Ames Research Center is complete as is the Mach 10 RCS testing
on Tunnel C at AEDC. Data continue to look good. The CFD for RCS testing correlateswell with the tunnel data.
In general, however, there is some discrepancy between Boeing's CFD and the
aerodynamic flow shown by the wind tunnels. LaRC's CFD matches the observed data
much better. It is generally felt that the mismatch is due to the chosen CFD grid and that
a little tv,eaking of the grid will bring things into alignment. This certainly points up the
23
JRF Engineering ServicesX-37 Monthly Report Februar_ 2001
Page 7
risks of depending totally on CFD (as Orbital Sciences did on Pegasus). Real data are
needed to anchor the analysis. Otherwise CFD can lead to erroneous conclusions. Once
your grid choice and other characteristics are anchored bv real data. the use of CFD to
expand the range of conditions becomes a powerful and cost effective tool.
The next tunnel entrv is scheduled for April in the Polvsonic tunnel. The purpose of these
tests will be to deal with details such as hinges, control surface gaps, etc. This _ill
conclude the currently' planned wind tunnel tests. Hov,ever, the Flight Sciences Lead
Engineer is continuing to push for one more entry' to investigate aerodynamics at high
altitudes, such as 250,000 ft. because he feels that knowledge in that regime is
insufficient and that a better understanding might be beneficial in solving some of the
trajectory questions discussed below.
Because of the weight problem, a Flight Sciences Tiger Team is investigating increasing
the weight capacity of the X-37. The two major limitations are entry heating x_ith
increased planform loading and w'heel touchdown loads. The team is looking at flying
the high heat rate portion of the trajectory at a higher angle of attack (hence the interest in
high altitude aerodynamics). The higher angle of attack should result in reduced heating.
It v,ill cost range and entry performance because of increased drag but there is no real
requirement for high range or cross range so this is probably' acceptable. It is probably'
possible to increase the wheel/tire size slightly* thus allowing an increase in landing
v,eight. The current best guess is an increase in allowable weight up to 7000 lbs. (vs. thecurrent 6800).
Launch Vehicle
The choice of launch vehicle is still in debate. Boeing management really favors the
ELV as an easier option for them. The greater line item cost of the ELV is a negative
but. as observed in the past, this begs the question of the hidden costs of Shuttle.
Boeing is coming close to defining launch vehicle-related requirements that will force X-
37 to use Delta IV Medium for the ELV option. In order to prevent that, NASA needs to
define requirements such that the characteristics of all possible candidates are enveloped.
In other words, specify such that, if X-37 meets the specifications, it can fly on any of the
candidates. This is commonly done with comsats where a particular model may fly on ahalf dozen different launch vehicles.
The enveloping specifications should include mechanical vibration, acoustics,
longitudinal and lateral accelerations, EMI, and probably others. A major discriminator
is the availability of an adequate size fairing since it is probably too difficult to go
enshrouded at this point.
JRF ENGINEERING SERVICES4023 Shadow Run
Las Cruces, NM 88011
(505) 532-9572 (phone/fax)e-maih [email protected]
31 March 2001
To:
From:
Subject:
Jay Laue, SAIC
Jim French
Monthly Report for 51arch
C: S. Turner, Lt. Col. Johannessen, M. Harris, J. Sisk, A. Nolen. T. Taylor. S. Stewart,
Maj. Titus. E. Nicks
X-40A
It has been decided that two captive flights with no problems are required before a free-
flight will be approved.
A computer problem occurred during flight preparation on 2 March and caused the flight
to be cancelled. The problem was a bit error related to the flash card. Three attempts
resulted in the same error. A power-off reset did not cure the problem. During
diagnostics, the error occurred again. The test was cancelled due to this problem and
weather. Later during further tests, the problem cleared itself.
A successful captive flight was conducted on 5 March. There were some problems with
short notice for personnel. Winds aloft were very strong making operations difficult.
The weather would not have permitted a free flight/also the case on 2 March). Four
successful passes were made. The dGPS performed well.
The Army crew became unexpectedly available, which opened the possibility of a captive
flight on 7 March, and a drop the following weekend. The 7 th flight was scrubbed due to
early weather and then a loss of telemetry services. The next plan was for Saturday the10 th.
A very successful captive flight occurred on 10 March. This cleared the way for a flee
flight on 14 March. The only obvious discrepancy was an unexplained fiat tire. No
problem on a captive flight but obviously undesirable for a free flight.
.3.5
JRF Engineering ServicesX-37 Monthl5 Report 31 March 2001Page 2
The only significant problem on the _/10 captive fli_oht, other than the flat tire. was a Ie_
GPS dropouts. The latter were determined to be caused by a lox_ number of GPS satellites
in view'. It would not have been acceptable for free flight. No problem has been found
,a'ith the tire. The entire assembly was replaced just to be sure.
Everything appeared to be "'Go" for a flight on the morning of Wednesday the 14 'h.
The first free-flight of the X-40A occurred at 0940 PST on 14 March on the second
attempt. Two dry' passes were conducted prior to attempting a hot or drop pass. The first
attempted hot pass was aborted because winds w_ere possibly out of tolerance at the
go/no-go point l although winds were okay at release time). The pass was continued
without a drop as a practiceA'erification run. The second pass experienced no problems.
Helicopter handling throughout was impressive in its precision.
The tree-flight appeared very smooth and solid on the video received at Seal Beach.
Although one person claimed to see a roll oscillation similar to that experienced during
the Holloman flight, it was so slight as to be invisible to the rest of us if indeed it
occurred. The previous oscillations were only about one degree, very difficult to detect
visually. The data do not appear to bear out the oscillation.
Touchdov, n appeared smooth with no obvious bounce. Rollout appeared well-controlled
and braking smooth. From the camera angle, it w'as difficult to tell how close to
centerline the vehicle was. but it was clearly in the rubber marks left by aircraft
operations. Later reports disclosed that it was about 15 feet off centerline at touchdov, n
and 7.9 feet off centerline at w,heel stop. At the latter point. C-MIGITS thought it v,as 2
feet off. Touchdown location along the runway was about 1250 feet.
Recovery operations appeared to encounter no problems.
Boeing had hoped to get approval for the next flight to occur on Wednesday. 3 April.
However the Range did not approve this and thus the alternate of 2 April was selected. If
all goes well, the next flight is planned for Saturday 6 April.
During handling of the X-40A after flight, creaking sound was heard. This turned out to
be caused by, a small disbond in some structure in the nose landing gear area. This has
been repaired.
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JRF Engineering ServicesX-37 Monthly Report 31 March 2001Page 3
X-37
Program
With the cancellation of the X-33 and X-34 efforts, there will be increased visibility of
the X-37 program and perhaps more help than we really want. The psychology of the
center and Headquarters management will be that this program has to work in order to
sho,_v that NASA in general and MSFC in particular can manage a successful X program.
The more support that can be garnered for the program the better. The vehicle is in
serious _aeight problems that must be solved for the mission to be successful. I strongly
recommend that v,e work closely with Boeing to try to develop a solution to the problem
as soon as possible.
It appears that, rightly or v,'rongly, Boeing was expecting the effort under 8-30 to be a
relatively simple extension of the current agreement and was taken by surprise by the
requirement to recast the proposal in a new format and rev, ork the budget to the extent
that they are doing.
I the review schedule for the rest of the program is as intense as has been reported to me.
it may be a valid question as to whether this is too much of a good thing. Without
knowing the details, it is difficult to assess, but it may be worth considering whether a
very intensive review schedule is cost-effective.
Vehicle Design
With the probability of changing to an ELV launch from the Shuttle. the vehicle will
probably become much lighter as various Shuttle-edicted redundancy and other hardware
is removed. This will help relieve the weight problem even if there continues to be only
one airframe. If we end up with two airframes, the second unit can be optimized for space
flight and include all the lessons learned on the first one. This will result in further weight
savings.
Flight Sciences
Data analysis of wind tunnel data continues. Things continue to look good except for the
previously discussed discrepancy in the Mach 6 to 10 regime. AEDC and NASA LaRC
tunnel data disagree with one another and with CFD. This discrepancy has yet to beresolved.
On a positive note, it appears that L/D at landing will be about 4.5. This is about 0.5
greater than expected. The increase will make the X-37 much easier to flare and land.
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JRF Engineering ServicesX-37 Monthly Report 31 March 2001Page 4
The entry into the Polvsonic Wind Tunnel has been pushed back to June. Since it is the
last planned tunnel entry, people keep adding test points the)' _ish to see. As a result the
test has _own much larger and more expensive. This is the main reason for the delay.
I have reviewed the preliminary report from the RCS test conducted in the NASA LaRC
and AEDC wind tunnels. I have been concerned about the possibility of dangerous
interactions between the jets and the airstream. Shockv, aves formed by' such an
interaction impinging upon aerodynamic surfaces can cause control problems. One such
interaction on X-33 required extensive reconfiguration of the RCS to preclude loss of
vehicle control. The tests on the X-37 models seem to put this concern to rest. While
there are strong interactions between the jets and the airstream, there is nothing that
indicates the sort of dangerous cross coupling seen on X-33. The data from the tunnels at
the tv,'o facilities compare well and both compare well to CFD analysis.
Models of the thrusters were tested prior to their incorporation into vehicle models to
ensure proper simulation and that the jets were well characterized. For these tests, the
jets used air. Innovative design approaches greatly simplified model changes test to test.
Since the forv, ard jets are not used on entQ', only aft jets were simulated. Because of
vehicle symmetry, it was not necessary to simulate all the aft jets. The models had
moveable control surfaces to investigate the significance of control deflection.
The relationship of jet interaction effect with angle of attack is non-linear but consistent.
There is no obvious correlation with sideslip angle. There is a Mach number effect that is
strongest at the lower end of the test range (M 2.5 to M 10). The momentum ratio of the
jet to the free stream appears to be a suitable jet interaction correlation parameter. Jet
interactions are affected by ruddervator motion on the same side. Flaperon and body flap
deflections are less significant. There is little or no impact of opposite side controls.
In general, the problem seems to be well understood and there should be no significantissues.
Structure
The repair of the lower fuselage skin section that was damaged upon removal from the
mold has been repaired. As noted previously, the repair consisted of cutting out the
honeycomb in the damaged lower corner areas and laminating new graphite epoxy layers
in the areas. NDE inspection of the repaired areas shows a few minor disbonds but
nothing significant. Work has proceeded on building up the structure even though a
decision to build up a second airframe would probably require some changes in thisairframe.
The suggestion has been made that. rather than building one more airframe for an orbital
vehicle and using the current repaired unit for the atmospheric tests, that two new
airframes be built and the current one scrapped. While the idea of having two new
_78
JRFEngineeringSen'icesX-37MonthlyReport31March2001Page5
airframesthat incorporateall the lessonslearnedfrom thefirst onebut donothaveall therepairsis attractive,it maynotbepracticalfrom thecostandscheduleviewpoint,h isestimatedthatbuildingasecondnewairframewouldaddabout6 monthstotheproiect,about4 of which is materialacquisition.
Therepairof thefirst unit is completeexceptfor repairof someminor separationsdiscoveredin NDE. Thisunit shouldbesoundandreadyto go I amtold.
Currently,furtherassemblyof theairframeison holdpendingsomemodificationsrequiredby loadsanalysis.Theaft framewasoriginally intendedto besecuredto theskinbybondingto thefacesheetof thehoneycombthatformstheskin.This joint maynotbesufficientlystrong.It maybenecessarytocut out the inner facesheetandhonevcombandlay in doublers(similar to what was done in the lower fuselage corners). Then the
frame would be installed using mechanical fasteners, resulting in a stronger joint. At last
report, a decision on whether to proceed with this change was being considered bv the
Chief Engineer.
Propulsion
A Rough Order of Magnitude estimate is being prepared for cost and schedule to resume
a full-scale composite tank effort. Again, 1 feel that it would be worthwhile to investigate
the technology being developed in the USFE program. That is a much more complex
tank than required for X-37.
Work at Rocketdyne was slowed to a crawl prior to the decision to retain the MPS. The
hardware was being boxed for storage and personnel were looking for new assignments
effective as of the completion of the storage preparation and documentation.
Subcontractors on tasks such as cutting the screens are being allowed to complete their
work. Rocketdyne has been directed to hold expenditures to the range between $0 and
$5000 per week.
The decision being made to get the AR2-3 program moving again, it appears that the
action may still be too slow to retain the current cadre of experienced personnel. In a few
weeks most will be gone and, very likely, not recoverable. As a result, corporate memory
and continuity will be lost. Rocketdyne has been told that they will be funded by 1 July.
This is too late to prevent loss of key personnel. It might be worth considering to provide
enough funding to retain one or two key people.
It appears that the Propulsion organization has agreement on the peroxide compatibilily
testing plan. I have not seen the new plan but expect that it is some what pared down
from the original version produced by the Tiger Team. As noted in an earlier report, that
version, while every test was w'orth doing, was probably more than was needed for X-37
3.,9
JRF Engineering ServicesX-37 Monthly Report 31 March 2001Page 6
Launch Vehicle
When Boeing resurrected the idea of flying on expendable vehicle recently. I reported
that their choice was the Delta IV Heavy. This is incorrect and was based upon my
misinterpretation of something I was told. I am indebted to Lt. Col. Johannessen for
pointing out the error. Delta IV Heavy was indeed a possible choice in an earlier study
under the assumption that X-37 could be dual manifested with another payload to defray
cost. At this point however the Delta IV Heavy configuration is uncertain and there are
even hints that it mav never be built. The chosen version at this point is a Delta IV
Medium 5-2. This means a common core booster with a 5 meter nose fairing and tv, o
solid rocket boosters. Boeing does state that, if Delta IV heavy comes to be. they would
consider it if they could find another compatible payload with which they could dual
manifest. The probability, of this is low.
It appears that the launch vehicle will be some version of Delta. I believe that this is a
good move since the Shuttle complicates things tremendously. The apparent campaign at
JSC to prevent the X-37 (and its hydrogen peroxide) from flying in Shuttle makes thingsmuch worse than normal.
The baseline Delta is the Delta IV Medium+ 5.2. However. it appears that there is a
viable possibility that one or two of the higher performing Delta II vehicles can do the
job. With the Delta II. it will be necessary for the X-37 to launch unshrouded. Flying
shrouded, as on Delta IV. makes life relatively simple. However. an unshrouded launch
will require extensive aerodynamics and possibly, even coordinating X-37 controls with
the Delta control system to perform load alleviation. One argument for going this route is
that the most likely' applications for an operational vehicle are unshrouded and this would
alloy, these issues to be addressed up front.
A dark horse candidate also is Sea Launch, which will have a 5 m shroud in the time
period of interest. Some concern exists about ITAR issues but it is felt that these can be
addressed by having the encapsulation done by Boeing personnel only.
G,N,&C
Guidance is looking good. No software is being written as yet but the subsystems are
becoming well characterized.
It may be necessary to go to larger motors on the actuators. The high rates required on the
body flap and ruddervators are causing unacceptable heating of the motor coils. Even
though not all actuators will require the larger motors, it may be that all the actuators will
be changed for commonality. The weight impact may be a factor.
The biggest problem worrying the G,N,&C is the B-52 aerodynamics and how it interacts
with the X-37. A severe wing drop and yaw is expected. This was experienced on X-15.
4-O
JRF Engineering Se_'icesX-37 Monthly Report 31 March 2001
Page 7
It is less of a problem for v,ingless vehicles like X-38. It _,,ould not be a big problem for
X-37 except for DFRC's insistence on dropping with controls locked.
JRF ENGINEERING SERVICES4023 Shadow Run
Las Cruces, NM 88011
(505) 532-9572 (phone/fax)e-maih [email protected]
To:
From:
Subject:
Jay Laue. SAICJim French
Monthly Report for April
28 April 2001
C: S. Turner. Lt. Col. Johannessen. M. Harris, J. Sisk, A. Nolen, T. Taylor, S. Stewart. J.
McDougal. Maj. Titus, E. Nicks
X-40A
it ,,,,as planned that Flt.2 would include an elevator doublet (nose up - nose down). Rt. 3
would include a rudder pulse and an aileron doublet. Rt. 4 would repeat inputs from 2 &
3 as required to get necessary data. Details of subsequent flights have not vet been
defined. If the early flights go well. some of those later flights may be cancelled.
Boeing began to consider what options might improve their chances of flight. One
question is. what could be done to increase the headwind placard values. The other
question involved using runway 04 rather than 22 and landing with a tailwind. This needs
to be looked at ver_.._vcarefully. Landing with a tailwind has lots of potential significance.
A taiiwind results in higher speed on the runway with impact on tires, brakes, and
stopping distance. It also raises the specter of overshooting the runway. Some aircraft act
a little squirrely in a downwind landing because of different ground effects. None of this
says it is a bad idea, just one to be handled with care.
On Thursday 12 April, X-40A was launched and fiew to a successful landing at about
0847 on the second hot pass. The PID was executed and was observed by gound
personnel. Landing appeared normal and very close to expected parameters.
Following the 2 nd flight, the team was prepared for another flight on Saturday 14 April or
Thursday' 19 April. The weather outlook for both days was poor.
A flight was attempted on 19 April but was scrubbed in flight because of winds aloft
being out of limits and because the RAJPO signal-to-noise ratio was unacceptably low.
42
JRF Engineering ServicesX-37 Monthly Report 28 April 2001Page 2
Initial investigation of the RAJPO problem did not uncover any' very specific ansv, ers. It
has been suggested that the cause was the current high level of solar activity.
The flight test scheduled for 24 April was cancelled because no helicopter pilot v,as
available. The test was rescheduled for Thursday 26 April. The flight, the third of the X-37 series, went off without a hitch. Touchdown was 10 feet to one side of centertine and
wheel stop 8 feet on the other side.
The helicopter is scheduled for maintenance over the 28/29 April weekend. Possible
dates for the next flight are Tuesday', 1 May, Thursday,, 3 May,. and Saturday 5, May. The
1 May date is doubtful because of the possibility of a Shuttle landing on the 2 nd. If the
next flight slips to Thursday the 3 rJ then the one after will be scheduled for the 8 th.
Work is progressing on getting some of the lakebed runv, avs operational again. Run_a avs
07/25 and 09/27 are candidates. Boeing is evaluating changes required to use these
runv, ays when they are read,,' but trying to minimize interference of this v,ith preparation
for the next flight.
X-37
Program
A Technical Interchange Meeting. in some sense a replacement for a CDR. took place on
3.4. and 5 April at Boeing Seal Beach. I participated primarily in the propulsion
meetings, but also visited meetings on the Thermal Protection System. GN & C andSoftware. and Structures and Materials.
The contract negotiations continue to drag on. There is evidence of concern among the
rank and file staff as to whether the project will actually go forward.
Vehicle Design
Very, little is happening as regards the weight of the orbital vehicle. Most of the attention
is focused on the Air-Launched Test Vehicle. Boeing is taking the approach that either
there will be two tail numbers, the ALTV and an orbital vehicle, or there will be nothing.
Therefore, the more immediate ALTV, for which the hardware actually exists, is
receiving most of the attention. While the weight is not as critical as for the orbital
vehicle, any weight increase has to fight its way on to the vehicle. This is very wise
because the nature of things is such that, as soon as weight is declared to be no problem,
the weight will immediately escalate until it becomes a problem. Keeping the lid on from
day one will not preclude growth but it will help control it.
4Y
JRF Engineering ServicesX-37 Monthly Report 28 April 2001Page 3
It is also true that the ability' to build a nev,' airframe that incorporates all the lessons from
the first one should allow a much lighter structure for the orbital vehicle. Nevertheless.
that vehicle is already overweight. The most stringent weight controls will be required to
keep vdthin weight limits. The new structure should help but it is not a panacea.
Flight Sciences
Work continues on refining the wind tunnel data. Detailed investigation of the results
from the tv,o tunnels indicates that the discrepancy there resulted from mach gradients
formed in the tunnels. At high angles of attack, greater blockage occurs then at lmver a-o-
a. Apparently the two tunnels reacted differently to this situation and produced the
discrepancies in data. Correction factors for the Mach gradients have been developed that
bring data from the t_vo tunnels into good agreement. Some of the errors in the [,aRC
data, involving incorrect lengths, have been corrected, further improving the correlationbetv, een the two tunnels.
CF"D is still out of agreement with the txvo tunnels. This continues to be investigated.
Most likely,, the problem lies in grid definition, specifically' in critical areas. It is vital that
the grids be defined properly so as to provide good correlation with the tunnels in the
Mach 6 to 10 regime since we will be more dependent on CFD in the higher speed
regimes that v, ind tunnels cannot reach.
Fortunately, hypersonic flow is fairly well behaved so that. once the grid is defined, the
CFD results for the higher Mach numbers can be believed. The chemistry and real gas
effects caused by heating do cause some concern but, in general, the results will be close.
This situation points up again the importance of having real wind tunnel or flight data to
anchor CFD analysis. As Orbital Sciences discovered to their dismay some years ago, un-
anchored CFD can lead to catastrophic results.
Structure and Materials
The planned C-SiC hot structure has encountered fabrication difficulties. Tests samples
to date have been deficient in strength by as much as 50%. Photomicrographs indicate
poor penetration of the SiC into the carbon fiber tows. The process involves first
depositing pyrolytic graphite on the fibers to provide a basis for the SiC to build up. The
SiC is deposited by infiltrating the parent gas into the fiber preforms. It appears that
neither the pyrolytic graphite nor the SiC is penetrating into all parts of the toy,. Part of
the problem may lie in the fact that 3K tow was used in the build up rather than 1K tow.
The numbers refer to the number of fibers in the tow,. The larger tows may limit
penetration of the gas. There are some data indicating loss of strength with carbon-
carbon using the large tow's, but not as severe as this. The difference may lie in the fact
that C-C is usually not made by gas infiltration but rather by saturating with resin, w'hich
JRF Engineering ServicesX-37 Monthly Report 28 April 2001Page 4
is then p_zolyzed. The wicking action with the liquid may drav, the liquid in more
readily.
Boeing, together with MSFC. is working the problem. It is important to reach a solution
since this is the first use of SiC in such structures. Failure could substantialh' set back
application of this material. It is possible to fall back to C-C but that would lose the
demonstration of SiC technology'. Actually, C-C is such a poor structural material that it
may not work in any case.
The PETI-5 body' flap is generally doing well although the full potential benefit will not
be obtained because of uncertainly in characteristics. This results from the data having
been obtained with materials from different sources. Also, the tendency of the titanium
core to dig into the fabric and draping of fabric into the core reduce strength.
Nevertheless this will provide good data on the use of PETI-5.
Failure of the original body flap design in tests has resulted in incorporation of acenterline rib.
The speed brake encountered serious "stop sign" flutter (by analysis) in its original form.
It has been redesigned to be stiffer by adding thicker core in the critical areas.
The possible change to the fuselage structure, as discussed in an earlier report, invohing
cutting away the inner skin and core and adding a multiple laver doubler to allm_ use ofmechanical fasteners to attach the aft frame will not be done on the first airframe. This
modification is only' required for orbital flight, not atmospheric. It is clear that Boeing is
betting on approval for a second airframe to use for orbital flight. This decision came out
late the week of 2 April.
Propulsion
The composite fuel tank does not appear to have major issues. The concept is a two-part
lay-up similar to the DC-XA hydrogen tank. Some possible areas of concern involve the
inner bellyband for joining the tv,'o hah, es.
Because the access opening is too small to admit a human, the inside belly' band cannot
be laid up in place as was done for the DC-XA tank. Rather, a form vdll be made
simulating the lower portion of the top hall This will be mated to the lower hall coated
with mold release and the bellyband laid up on it and the lower half and cured to the
latter. The mold is then removed, the top half moved into place and the joint cured under
vacuum bag. Some concern was expressed about this approach but it seems the most
practical solution in this situation. Good NDE and proof test should reduce the concern.
The other issue is the use of bonded-on fittings to interface the tank to the vehicle
structure. This approach was chosen primarily to avoid fastener penetrations through the
45
JRF Engineering Service,_X-37 Monthl) Report 28 April 2001Page 5
tank wall. Preparation and procedures is critical in achieving adequate joint strength.
Many of the joints will be loaded in peel, the most difficult for a bonded fitting.
There appears to be no significant issues with the oxidizer tank. It is a spun and v,elded
5254-H32 aluminum structure. Welded on pads allov_ for mechanical attachment of the
longerons that interface to the airframe. The alloy is work hardened and v,elding causes a
loss of properties, which must be compensated for in design.
The RCS tank is now 6061 aluminum (as reported a fev, weeks ago). This is only true of
the non-v, etted section that is protected from peroxide bv the silastic bladder. The sump.
exposed to peroxide, is still 5254. This change saves 4 to 14 lbs. depending upon the
optimism applied to 5254 properties.
In the rest of the system, lines, fittings, and valve bodies are stainless steel, a Class 2
material. Where possible, peroxide exposed surfaces are electropolished to reduce
activity. One problem is the presence of a magnetic 400-series stainless steel. This is
required in the latching valves for the latching function. Boeing is evaluating coatingssuch as zirconium nitride allow use of this material.
The problem v,ith loss of control of NEAR in its first Eros rendezvous was possibly
caused by poor propellant slosh modeling. X-37 uses the same mechanical models.
which are something of an industry' standard, however, the presence of extensive baffling
in the tank and development of a coupled GN&C/slosh model should relieve thoseconcerns.
Analysis indicates that most operations are low risk, hoxvever: propellant transfer is rated
as medium and propellant dump as high risk. The former is considered risky because of
limited to no experience with very lov, flow rate transfer in zero-g. The propellant dump
may be high risk because of several factors: the unknown behavior of high flm,v liquid
streams flow'ing into vacuum, the possibility of propellant ice forming and possibly
recontacting the vehicle immediately or a few orbits later, and possible chemical attackon the TPS or adhesive.
There is also a concern regarding accurate control of peroxide loaded into the RCS tank.
A ne,a wrinkle is the use of the axial thrusters to trim out residuals from the MPS burns.
This is because the MPS acceleration is relatively high and results in some uncertainty in
actual deltaV. The MPS will be programmed to burn slightly short so that a positive
makeup deltaV will be required. If both axials fire properly, there is no problem. If one
fails but the other fires, the RCS can take out the asymmetric thrust torque and the
accelerometer will allow a longer burn to obtain the desired deltaV. If both axials
thrusters fail, the two yaw thrusters are canted aft by 30 degrees thus providing an axial
component of thrust. To take advantage of this option, the control system must be
programmed to use the canted thrusters if it detects no response from the axial thrusters.
4_
JRF Engineenng ServicesX-37 Monthly Report 28 April 2001Page 6
When I asked about this, it appeared that Boeing had not thought about it. so it may be
something to watch in the future.
The AR2-3 engine program is in good shape as far as hard_aare is concerned. All catalyst
screens were completed before the stand down discussed below. This is prudent given
the amount of art as well as science involved. The screens still require the samarium
nitrate dip but that is straightforward. Controller boards are complete except for the
spare. Some minor damage needs to be polished out of turbine blades. The turbo
machinery, has been inspected and checked out.
The AR2-3 program continues on hold. All personnel have been reassigned to other
programs. Their availability on the proposed 1 July start date is open to question. It is
hoped that the Chief Engineer can be recovered but that is not certain.
The RCS system is close to beginning tests of some hardware. Test plans are being
developed and v, ork may start in a fev, v_:eeks. There is some concern that Boeing is not
really' ready to begin this activity given the uncertainty' of the schedule.
A major set of study' topics involves analysis of the propellant transfer and dump
activities as well as propellant gauging. There are several aspects of this to be looked at.
One is the operational aspects of how it is done. how it is controlled, how repeatable, etc.
Boeing's analytical tools will be improved for this analysis. At the same time. the system
and process is being carefully' examined for single-point failures.
G,N,&C
I have revie_ved the softy, are validation and verification information from the TIM.
While I am not an expert in the field, it appears that their approach is good and. if
thoroughly, implemented, should yield a satisfactory result. It is similar to the \vav
soft,rare was done on the highly, successful DC-X/XA programs and of course is being
validated by the X-40A flights.
I remain very concerned about DFRC's insistence that the X-37 be dropped from the B-
52 with controls locked. The analysis to date verifies the anecdotal information that the
X-37 will be strongly affected by the B-52 flow field and can undergo extreme attitude
excursions even during the 1-second period of locked controls now proposed. It would
appear that there is serious risk that the vehicle could depart controlled flight. Even if it
manages to recover, the possibility of extreme attitudes is most undesirable, if nothing
else. considerable loss of altitude is possible. This could have very serious effects on the
flight profile.
The new aerodynamic data from Flight Sciences are being passed to the G,N.&C group
for evaluation and inclusion in the software. There will probably be no major changes as
a result of this but rather refinements of the existing parameters.
.47
JRF Engineering ServicesX-37 Monthly Report 28 April 2001Page 7
The success of the X-40A flights has greatly' increased the confidence that the vehicle is
v_'ell understood, at least in the lov, speed regime.
Bv all indications, the X-37 has adequate trim and control authority in the various flight
regimes. The high-mounted butterfly' tail in conjunction v,ith a wing shov_ s some
advantage over a delta planform in that it gains control authority at higher angle of attack
and thus avoids the tendency to flip over sometime encountered by delta shapes if a
critical angle of attack is exceeded.
48
JRF ENGINEERING SERVICES
4023 Shado,_ Run
Las Cruces, NM 88011
(505) 532-9572 (phone/fax)e-maih [email protected]
26 May 2001
To: Jay LaueFrom: Jim French
Subject: Monthly Report for May 2001
C: S. Turner. Lt. Col. Johannessen, M. Harris. J. Sisk, A. Nolen. T. Taylor, S. Stex_art, J.
Mac Dougal. Maj. Titus, E. Nicks
X-40A
The X-40A plan was for 7 flights total. As was suggested in an earlier report, the
possibility of canceling one or two of those flights, if sufficient good quality' data were
obtained on the earlier flights, would have been considered if the schedule seemed to
stretch unacceptably. The Army planned on taking the helicopter back about 18 May.
vdth the possibility of an extension if, say, there was one more flight to go. Getting the
seventh flight in before the 18 th required three flights in two weeks, a frequency' not
previously demonstrated. Fortunately. there was some tendency bv the range to be more
lenient in allowing flights to be scheduled since the X-40A starts early and clears the
runw'ay quickly. The team rose to the occasion most admirably.
The need to support a possible Shuttle landing precluded a flight on 1 May. The weather
was perfect and it would have been a good day to fly. The goal was to get at least one
flight offduring the week. Thursday, 3 May was originally targeted with a backup of
Saturday 5 May. However. the Thursday date was scrubbed leaving Saturday as the
primary. The fourth flight under the X-37 program was successfully conducted on that
date. Winds were 2 to 4 mph. The flight featured increased lateral PIDs and was to
release 200 ft. high or low. depending on wind. The next flight was scheduled for 8 May,.
Flight number 5 of the X-37 series was successfully conducted on 8 May. The main goal
for the last two flights was crosswind landing so weather was important as was runway
selection. Flight 6 was scheduled for Friday 11 May with Saturday as a backup. It was
not possible to fly on either day. On the 1 l th. no wind data were available because the
data taker overslept. On the 12 th, the winds at altitude were too high for the drogue chute.
4Y
JRF Engineering ServicesX-37 Monthly Report May 2001Page 2
The shear tie problem referred to in earlier reports came about through human error
caused by over-tightening the front pads that hold the X-40A in position on the
strongback. The ties between the vehicle skin and internal bulkhead were cracked. The
situation is well explained in a short report by Dale Shell of Schafer Corp.
The issue of crossw ind landing is interesting w'ith this vehicle. The relatively fat fuselage
and very small v,ings tend to mean that there could be some blanking of the dov,nv,ind
wing with a strong crossw'ind. Given the very high landing speed, this does not seem a
big problem however.
There are tv, o classical crosswind landing techniques. One is to come down final in a
lbrv,ard slip tcross controlled rudder and aileron), which keeps the vehicle aligned _ith
the runv, av while flying a little sidev,ays relative to the airflow. This slip is held until
touchdo_vn. Alternatively. the vehicle is flow'n in a crab. that is, heading into the relative
_ind, until just before touchdov,n. This means that the vehicle axis is not aligned with the
runway. An abrupt rudder input turns the vehicle so that its long axis is aligned with the
runv, ay at touchdov,n. The X-40A will fly the final descent crabbed into the x_ind.
Hov, ever. rather than a control movement to straighten it out before touchdoxvn, it _ill be
allowed to touch in the crabbed attitude. The landing gear will then pull it straight. This
departure from the classical technique is because it is difficult for the guidance svstem to
kno_ the altitude accurately' enough to perform the maneuver at the optimum altitude.
Too early and the vehicle will build up a sideward drift before touchdov, n. Too late and
it lands in a crab anyhow. The Shuttle uses the same technique and gear sideloads is oneof the limitations on Shuttle crosswind.
X-37 v, ill have much better crosswind capability than X-40A because the gear track iswider.
Judging the flare altitude on this vehicle is very critical because of the high sink rate and
low IJD aggravated by the small size. While Shuttle has similar characteristics, the very
large planform area gives a substantial ground effect that tends to cushion any errors.
The X-37/X-40 shape, with its very small wings and small size has very limited ground
effect so timing the flare is much more critical.
In order to get more of a crossvvind component, the team v,'anted to fly into iakebed
runway 17. This was impossible because of the requirement to redo Ec calculations and
to obtain the various approvals. It was thus necessary to continue using the hard surface
runway 22 and hope for crosswinds. Boeing calculates that X--10A can handle up to 15 kt
crosswind component and would like to actually test it up to 12.5 kt. It seem ironic that,
having fought so hard to get permission to use the hard surface runway, now it can't be
changed. Chuck Yeager didn't kno_: how easy he had it in 1946.
The team requested two windows each day for the week of 14 May in hope of completing
the flight plan. During the return to base from the aborted mission on 12 May, RAJPO
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JRF Engineering ServicesX-37 Monthly' Report Ma,, 2001Page 3
dropped out tw'ice. During preparations for the scheduled 15 May flight it appeared that
RAJPO could not see the X-40A at all. This problem v,as resolved in time for an earl,,
morning attempt on 16 May. The problem apparently had to do primarily v, ith the
location of the vehicle. And did not appear to be X-37 related at all.
The sixth flight under the X-37 program was successfully conducted on 16 May. The
flight plan included a long PID maneuver. A crosswind up to 12.5 kt was desired for this
flight but was not mandatory. Initially, the crosswind looked as if it might be close to the
desired level for Flight 6. Hov, ever, it appears that the wind dropped slightly, about
release time so that. at first look. it is believed that about a 5kt crossv, ind component was
experienced. Touchdov,'n accuracy seemed to be very good.
Most of the rest of the week was available for Flight 7 except for a possible conflict
Friday morning. The test was scheduled for Friday' morning but that attempt was
cancelled due to wind shears in excess of acceptable values.
Flight 7 was successfully conducted on the morning of Saturday', 19 Ma_. To add a bit of
drama to the flight. CMIGITS lost GPS 2 sec. after release. The entire flight v, as made on
inertial guidance. Preliminary' numbers for landing accuracy look just as good as those
flights made with GPS. At this point there is no word on the amount of cross v, ind.
CMIGITS came back on line just after touchdown.
This concludes the effort on X-40A under the X-37 program. Even though it is
substantially behind schedule, it v,as nevertheless a successful program. Boeing's
G.N.&C group feel that they have learned a significant amount regarding the 1o_-speed
aerodynamics and controllability of the configuration. In addition, a successful flight test
series cannot help but improve the morale.
X-37
Prot_ram
Some of the IPT leads are concerned by the possible additional 4 months program
duration that is understood to be part of the NRA8-30 package. Budgets were done based
upon the previous schedule (w'hich was slipped four months from the original). In order
to accommodate the additional four months, they will either have to reduce personnel or
ask for more money.
Vehicle Design
Z�
JRF Engineering Se_'icesX-37 Monthly Report May 2001Page 4
Boeing questioned the validity of flying a composite fuel tank. The chosen material is
well known and w'idely used in this application so no nev, technology' is being
demonstrated. Because of minimum ply considerations in a filament wound composite
tank. it was considered quite possible that an aluminum tank would be lighter than a
composite in this size range. Given the simple shape, it was almost certainh' be cheaper.
The real interest in composite tanks v,'as for the peroxide since fuel v, as deemed no
problem. The composite oxidizer tank has been out of the system for a year. When the,,
asked mv advice on the subject. I agreed that it made sense to drop the composite fueltank.
The cost and weight advantages of the aluminum tank appeared valid, so. _aith MSFC
agreement, the requirement for a composite fuel tank was dropped. Paperv, ork has been
initiated to change the fuel tank from composite to aluminum.
V_eight is holding reasonably' steady, for the moment. The weights people are watching
very closely to try to prevent any surprises. The decision on the program and hardv,are
changes proposed in NRA 8-30 will be very critical of course.
Propulsion
Rocketdyne is completely' out of money and the team is dispersed. The technicians who
have done the engine assembly have been laid off and the turbomachinery engineer has
resigned. While I understand the fiscal problems that have led to this situation (including
Rocketdvne's persistent cost overruns), I continue to fear that loss of key, personnel may
cause severe problems in the future. The long-term cost may completely' overshadow any'
current savings.
Rocketdyne's restart has now been delayed from 1 June to 1 July. The one bright spot in
that area is that it looks as if the AR2-3 Chief Engineer and one other major player will
become available from their current programs during the summer so it mav be possible to
reconstitute the core of the team. I hope that funding becomes available in time to get
these critical individuals back on the program.
One of the concerns incident upon the stretchout of the schedule resulting from budget
limitations is the impact on small suppliers. Large subcontractors have enough business
base to tolerate delays and changes but small companies find such situations difficult and
sometimes fatal. A case in point that has concerned Boeing is Castor. the valve supplier.
In response to this concern, a partial FDR was held at Castor. This allow'ed Boeing to
make a program payment, which will help keep Castor going. A delta FDR may be
required later to cover what was left out of this one.
..3-2
JRF Engineering ServicesX-37 Monthly Report Ma_ 2001Page 5
TPS
As reported earlier, arc jet tests at the predicted heat flux causes slumping of the leading
edge TPS. This is not sufficient to cause failure, but may cause some problems as
discussed under Flight Sciences. The TPS personnel think there is a fair chance that no
slumping will occur since the aeroheating analysts tend to be very conservative.
Boeing is v`orking on development of new processes for making the RCG coating for the
v`ing leading edge tiles. The suppliers that made the material for Shuttle are no longer
qualified. The Shuttle program is looking to qualify a new source since eventually their
current supplies v,ill run out. Hov`,ever, they are looking for a new supply two or three
years from now. X-37 needs one much sooner, thus the desire to develop a simpler in-
house process. They v,ould like to get it done in time to qualify, the material for X-37 in
the near term. If the tests are done using RCG material borrowed from Shuttle and then a
nev, process is developed, the qualification v`ill have to be repeated. It v`ould obviously
be better to get the new process developed sooner. Right nov,, X-37 is borrov`ing from
Shuttle and it is not clear how long that can continue. Independence is very desirable.
It might be argued that technology development in this area has not been successful since
it is predicted that the TPS cannot stand the entry environment. In fact. Boeing and
NASA have made significant strides in increasing the capability' of TPS tiles over the
current state of the art. It is just that the v`ing leading edge environment on X-37 is so
severe that the tiles still cannot survive as reusable units (assuming the temperature and
heat flux predictions are correct). The major culprit is the small leading edge radius of the
airfoil, a result of the small size of the X-37. I suspect that these tiles v,ould be much
more successful on the leading edge of a Shuttle.
G,N, & C
Some time ago it was mentioned that weight could be saved by changing the philosophy
of using the same type of actuator for all functions on the vehicle. Rather the actuators
would be more nearly customized, using standard components such as motors, gear
boxes, etc. This has nov,, been done and has resulted in saving weight. No cost data are
available but it is probable that the penalty is not great since all components are standard.
There appears to be some hope of a solution to the B-52 clearance problem. It appears
that. if X-37 drops with the body flap locked in the full dov`n position for the first second,
there is no way that X-37 can recontact the B-52 no matter what the other controlsurfaces do.
If DFRC accepts this (and they appear favorable to doing so) then it will not be necessary
to lock the controls at release except for the body flap. The flaperons and ruddervators
are then free to control vehicle attitude disturbances caused by the B-52 flow field even
as the body flap causes steep pitchdown to avoid the B-52.
5-_?
JRF Engineering ServicesX-37 Monthly' Report May' 2001Page 6
The new issue t there is alv_'avs a new issue) concerns reactivating the body' flap. It can be
run to the full nose dov,n position and power removed. Power removal will cause it to
lock in place. After the first second, pov,,er will be reapplied and the flap moved to the
proper trim position for flight. The issue relates to how the power is applied. Boeing
wants to simply program the flight computer to power up the actuator at the proper time.
Safety finds a softy, are solution unacceptable. They, want a separation-initiated timer.
While this will cost a little ,xeight and money, my inclination is to do it that wav. It v, ill
be cheaper in the long run than another protracted battle with DFRC over safety.
Conclusion of the X-40A flights should free up personnel to work on X-37.
Flight Sciences
The resolution of the discrepancy' between the wind tunnels and CFD is progressing.
Some additional corrections to the LaRC wind tunnel seem justified. Boeing will be
meeting v, ith LaRC to discuss this since too many corrections begin to sound like "'dry-
labbing'" the data and the Flight Sciences lead w'ants to avoid that.
As suggested in earlier reports, revision of the CFD grid is needed to improve the fidelity,
of that simulation. Evidently. when the CFD analysts laid out the grid for the high mach
regime, they' used a similar grid to that which was used in the lov, er speed regime. This
v_as not a good idea. The lov, er speed operation occurs at lov, er altitude where the higher
density means a higher Reynolds Number and a thick boundary layer. The high density
gridding is really' only' needed in the boundary laver. Unfortunately. the higher Mach
operation occurs at much higher altitude, which leads to a lov, er Reynolds Number and a
much thicker boundary, layer. In fact the laminar boundary layer may reach almost all the
wav out to the shock. The upshot of all this is that the high density gridding needs to
reach much farther from the vehicle in the high altitude/high Mach number regime in
order to get a good result. This requires a lot more computation time than the lov, er
altitude model, but is necessary if the CFD results are to be depended upon. The small
size of X-37 compared to Shuttle exacerbates the Reynolds Number issue.
As noted above, the results of arc tunnel tests showing that there may be slumping of the
TPS on the wing leading edges are a concern. As the TPS slumps, a ridge builds up aft of
the stagnation point. This could have detrimental effects upon the airflow. Tripping of
the laminar boundary layer could cause increased heating on the wing. It may also effect
the pressure distribution that could result in loss of lift or even control problems. It might
affect stall angle of attack, which could cause landing problems. Because of these
concerns, the upcoming wind tunnel tests will simulate the ridge caused by, slumping to
determine if there are any detrimental effects. If not, we can proceed as planned. If any
of the possible problems are, in fact, observed, some solution will be required. In any
case, the leading edge will have to be replaced after each flight if it slumps. This is not adesirable feature in a reusable vehicle.
.34
JRFEngineeringServicesX-37MonthlyReportMax2001Page7
Muchof theheatingproblemagainresultsfrom thesmallsize. While the v,ing is
relatively blunt, the small size results in a small radius of curvature. This, in turn causes
heating problems. The Shuttle also experiences shock impingement heating on the
leading edges, but the much larger size reduces the heating problem. While the X-37
planform has some virtues, one v,onders if it is the best option for a small vehicle. A
wingless entry vehicle with vertical landing capability would avoid most of these
problems.
Flight Operations
A series of range safety' meetings is working through the issues with FTS. This seems to
be going fairly well. If the decision comes dov,n to switch to an ELV for launch, some of
it will have to be redone but much v,ill remain applicable. Some new items such as a
propellant tank destruct charge vdll have to be added.
It is currently planned that X-37 would pick up the FTS receiver units that were being
built bv L3 Corn for the nov,-cancelled X-33 program, h appears that the only required
modification would be to change the tones. This would save about 3 months for the X-37.
5-3-
JRF ENGINEERING SERVICES4023 Shadow Run
Las Cruces. NM 88011
(505) 532-9572 (phone/fax)e-maih [email protected]
30 June 2001
To:
From:
Subject:
Edgar W. NicksJim French
Monthly Report for 30 June 2001
C: S. Turner, Lt. Col. Johannessen. M. Harris, J. Sisk. A. Nolen, T. Taylor. S. Stewart,
Maj. Titus
X-40A
Analysis of the X-40A flight test data is in work. St. Louis is carrying out the
aeromaneuver analysis. So far everything looks good. The data being obtained will feedin to the X-37 work.
The test crew took a week's rest after the final flight, then came back to pack up and ship
the vehicle and support equipment back to Seal Beach. A couple of items borrowed from
DFRC have been removed. Dummy hardware and run-out batteries will be used to
replace some of the removed parts when the vehicle and FOCC go on display.
The X-40A has been returned to Seal Beach and currently' is in flyable storage in Bldg.
91. It vdll presumably be placed on display at some time in the future.
CADS wind tunnel and flight test data agree very well.
A debriefing is being prepared by G,N,&C for the flight test program. Target date for
completion is mid-August.
JRFEngineeringServicesX-37MonthlyReport30June2001Page2
X-37
Program
With the word no_a out that X-37 will receive no funding from NRA8-33. the v, ork at
Boeing was cut back to about 65% of the former level. Since this is on Boeing's money.
it is uncertain how long this will continue, although a period of about 2 months is
rumored. Staffing has been cut back in essentially all areas.
Boeing program personnel are primarily keeping busy responding to the various
programmatic options and questions generated as part of the on-going negotiations v,ith
NASA. More personnel are being reassigned to other projects.
Morale is very lov, at the moment. Uncertainty continues to take its toll. The possibility
that some critical tasks may be allowed additional funding in order to keep the project
moving and to retain vital personnel is generating some enthusiasm v, ithin the Boeing
team. For improved morale everyone needs to feel that we are making progress.
More and more frequently in my discussions with Boeing lead personnel, I hear voiced
the same concern that I surfaced sometime back in these reports, namely the difficulty in
restarting the effort after an extended slow dov, n and after people have been farmed out to
other projects. The corollary to that concern is the cost inherent in the delay. As has been
stated previously, no one should assume that the previously planned budgets will hold in
the face of a long slowdown. It is simply not possible.
I am sure that readers of these reports are weary of hearing such seemingly' negativecomments, however. I feel that it is vital for these words to be said. no matter ho_
unpleasant they may be.
Vehicle Design
Work presently is being concentrated on the B-52 drop test vehicle. Little or nothing is
going into the orbital vehicle until something is decided as to the future of the program.
A major question that needs to be worked is: how' man}, airframes? Originally, of course
there was to be only one. That led to some problems since various repairs and simple lack
of experience led to the airframe being undesirably heavy. When it was hoped that
additional funding would be forthcoming from SL1. two airframes were included in the
program. The first airframe then became the air-launched test vehicle (ALTV). Since
most space-related systems ,xere missing from ALTV, weight v,as not a problem and
some weight-saving options were not invoked in order to ease schedule and budget, it
was assumed, probably correctly, that the second airframe would be lighter and more
37
JRF Engineenng ServicesX-37 Monthly Report 30 June 2001
Page 3
suitable for orbital flight. The disappointing result of the SLI av`ards, hov`ever, have
probably eliminated a two airframe option. There is nov, a degree of uncertainty' v`ithin
Boeing at the v,orking level as to v,hat the approach v,ill be, assuming that the lending
difficulty is resolved sufficiently' to let the project progress. Do they proceed under the
assumption that the presently, existing airframe is ALTV only' or that it may be called
upon to do both missions7
The weight of the orbital vehicle continues to hold stead,,,'. In fact, it has gone dov`n
slightly, to about 6686 lb. Potential increases at 304 to 418 lb still exceed the potential
reductions at 160 lb. These numbers are based upon Shuttle requirements. Svdtching to
an ELV should allow significant reduction in v,'eight. The ALTV is at a comfortable 5759
lb. These data are from early in the month and may, have changed slightly'.
FliRht Sciences
This area is being particularly hard hit. The team had largely, completed the lov` speed
aerodynamics v,ork and were concentrating on the high Mach number regime. V,/ith the
decision to put all the high speed (i.e. orbital entry) v`'ork on hold, much of their current
v`ork has been halted. Personnel have been cut 75C7c in Flight Sciences.
The wind tunnel entry planned for this summer v`ill go ahead but v,ill concentrate on lov`
speed v`ork. If the program does in fact return to its original plan, it v`ill probably' be
necessary to do another tunnel series to fill in the gaps in the high speed regime.
Work is continuing on lov` speed aerodynamics in support of the ALTV. The lead
engineer is concerned about the rapidity' with w'hich he can restaff and get the activity
ramped up when a go-ahead is received. This is a particular concern in that Flight
Sciences needs to be in the lead relative to some of the other disciplines since the latter
(e.g. G,N.&C) depend upon Flight Sciences for information. Delay, s in G.N,&C would in
turn impact avionics and software.
The previously reported discrepancy in the Mach 6-10 regime is still not fully resolved.
All the corrected wind tunnel data have been received from LaRC. The current slowdov`n
has prevented any analysis being done at Boeing to resolve the discrepancy since all high
speed work is on hold.
All v`ork has stopped on RCS tasks.
G, N, & C
The team is nov`, concentrating on the B-52 drop test controls. About 3 people (out of 16
total) have been displaced due to the slowdown. These are people who are primarily
involved in the orbital mission. These people will be placed on short term temporary
.5a'
JRF Engineering ServicesX-37 Monthly Report 30 June 2001
Page 4
tasks in an effort to keep them available for a quick return when the orbital effort picks
up again.
Softw'are work in support of ALTV is moving along well. The first release is planned for
mid-August.
As discussed in earlier reports, the concern regarding possible recontact with the B-52 is.
probably, solved. With the body' flap locked in the nose dow, n position, the other surfaces
cannot do anything that v,ill cause the X-37 to hit the B-52. Everyone seems to accept
this. The only problem is to agree upon the means to lock the body flap actuator in
position. Fortunately, Range Safety seems to agree that removing power from the
actuator is sufficient. They are apparently convinced that the brake will hold the actuator.
and thus the flap, in place so long as there is no power. This avoids the necessity of any
kind of mechanical lock. How, ever. powering off the actuator via the control softx_ are is
not acceptable. An additional switch will be required, v,hich v,ill be actuated a second or
so after drop to allow power to the body flap actuator. This will add some weight and cost
but is probably, the least painful answer.
The problems with the electromechanical actuators for the control surfaces seem to
coming under control. The vendor appears to be w_orking well. The actuators are
customized to some degree to save weight as opposed to all being the same. Generally
speaking the motors are all the same but v,ith different gear boxes. The concerns about
actuator heating have pretty much gone away.
TPS
Work on the high temperature TPS has stopped, however, TPS work goes on. Since the
ALTV must have the same external shape as the orbital vehicle, it is necessary to have
surrogate TPS tiles, blankets, etc. to fill up the space that the real TPS would ultimately
fill. This requires design work just as does the real TPS. The work is not wasted since
much of the design will translate directly to the real TPS.
The ALTV will require some actual TPS in a few locations. The antennas on the ALTV
will be the same as on the orbital version. Since they v,ill have to look through the TPS
on the orbital vehicle, it is necessary to have them do the same on the ALTV in order to
evaluate the effect on gain, pattern, etc. For this kind of testing, a surrogate would have to
approximate the real thing so closely that it is easier to use the real TPS.
The concern about the effect of the continuing delays surfaces here as well. Test slots
reserved for X-37 TPS tests are being lost as their dates come and go or as the times are
assigned to other programs since X-37 cannot state when they will be able to test.
Similarly', agreements had been made to borrow various test fixtures in order to keep
costs down. With the delays, many of these fixtures will go on to other tasks. This may
53
JRF Engineering Sen'icesX-37 Monthly Report 30 June 2001
Page 5
require X-37 to design and build its ov,n fixtures. This w'ill have schedule and cost
implications.
Propulsion
Main propulsion is almost entirely on hold. The lead engineer has gone to another proiect
and at least most of the subcontractors have received at least verbal stop work orders. The
remaining staff is addressing issues of termination liability. ARC. the RCS thruster
provider, spent about S250K of their IR&D on X-37 and are asking to be reimbursed for
it. I suspect others vdll want the same.
In addition to the above, of the two people left on X-37 propulsion, one is working on
Action Items from the TIM and whatever other tasks there are and the other is v, orking
on the proposal to NASA. All contracted work is stopped.
During my visit to Boeing. I picked up a rumor that NASA is looking at the possibility, of
going to a monopropellant hvdrazine deorbit and RCS system. I assume that this arises
from the irrational fear of hydrogen peroxide that pervades some parts of NASA. It ,,,,as
okay for John Glenn and the other Mercury astronauts to use it but somehov, it has
become more dangerous in the ensuing 40 years. While going to a hvdrazine system is
possible, people should be aware that such a change this late in the program will also
have cost and schedule impact. It is also worthy of note that qualifying peroxide ,`vas one
of the goals of this effort.
Electronics and Software
As in the other subsystem areas most of the work not directly connected to the ALTV isslowed down or on hold.
Flight Operations
A meeting was held at Boeing that included personnel from SMCTD. USAF FTC.
DFRC. and others to discuss future flight operations. A major subject was the flight test
approval process. There was also discussion of the flight test plan. These meetings will be
quite valuable as the program moves forv,ard since there will no doubt be a lot of
pressure to make up the time lost in the slowdown.
60
JRF ENGINEERING SERVICES
4023 Shadow Run
Las Cruces. NM 88011
(505) 532-9572 (phone/fax)e-mail: [email protected]
To:
From:
Subject:
Edgar W. NicksJim French
Monthly Report for 28 July 2001
28 July 2001
C: S. Turner. Lt. Col, Johannessen. M. Harris. J. Sisk. A. Nolen. T. Taylor. S. Ste_vart.
Lt. Col. Kastenholz
Note: there was no weekly report for the week ending 21 July because of" vacation.
X-40A
The flight test report for X-40A is still scheduled for release in mid-August. Work on itwill resume after release of the soflware discussed belo_.
X-37
Program
The visit of USAF generals to Boeing apparently went well. Only two showed up. Gen.
Hamil apparently being unavailable. According to Boeing personnel, the visitors had a
great many detail questions about the project. One topic in which there was considerable
interest was whether or not two orbital flights are sufficient to obtain the desired data.
The obvious answer is "No" since, with the complexity of the entry environment and the
various control interactions, etc. several flights would be necessary to even begin to open
the envelope. The rather arbitrary definition of four Shuttle flights as "Test Flights" with
all subsequent being "Operational" was much more politically motivated than grounded
in engineering. Many people consider the Shuttle still experimental.
#/
JRF ENGINEERING SERVICES4023 Shado'_ Run
Las Cruces, NM 88011
(505) 532-9572 (phone/fax)e-maih [email protected]
01 September 2001
To:
From:
Subject:
Jay Laue
Jim French
Monthly Report for August 2001
C: S. Turner, Lt. Col. Johannessen, M. Harris, J. Sisk, A. Nolen. T. Taylor. S. Stewart.
Lt. Col. Kastenholz. E. Nicks
X-37
Program
The Boeing staff is continuing to prepare briefings for USAF and Aerospace and to
perform analysis to support the trade studies. They are also in the process of updating the
project plan.
1 have made no contact with Boeing during the latter part of the month, so most of the
Boeing activity discussed below relates to activity early in the month. Most of my
activity during the month focused on the Propulsion Trade Study as discussed below.
Because of conflicts, I have been unable to participate in the ALTV Trade Study telecons
to an}' great extent but have reviewed documentation as it was sent to me.
G,N,&C
The Release 2 software for the B-52 ALTV was completed and released to the software
people late in July. This is software lbr a single string system to be used in the Simulation
Lab. The software group is writing the hand-generated code that goes with the autocoded
output from the G,N. & C group. The package was to be ready to pass on to the Sim Lab
in mid to late August..
d2
JRF Engineering ServicesX-37 Monthly Report 1 Sept. 2001
Page 2
G,N, & C is now v¢orking on the Release 3 package which is a three-string version v,ith
substantially better sensor information.
The flight controls people are working on flexibility models to be incoporated in the codelater.
Qualification testing of the SIGI guidance package was in progress early in the month.
One Boeing engineer is in residence at the supplier for the duration of this activity.
Flight Sciences
Nothing new to report. Continuing to wrap up the subsonic data.
Propulsion
The propulsion group is looking at several options:
The AR2-3 with hydrogen peroxide monopropellant RCS
An all monopropellant hydrogen peroxide RCS and OMS
An all monopropellant hydrazine RCS and OMS
A bipropellant NTO/hvdrazine engine vdth hydrazine monopropellant RCS
These four options are the remainder of a much larger suite of possibilities originally
suggested. See below.
This activity is in support of the Propulsion Trade Study. 1 strongly remain an advocate of
sticking with the baseline system because, I believe, it offers the maximum propulsion
technology advance. The options using conventional storables will teach us nothing new
in the propulsion arena. Clearly, there are arguments for the other approaches Inot the
least of which is cost) but I feel that the baseline should be retained if possible,
Propulsion Trade Studies
There was considerable discussion of the DRM descriptions and the implications of
meeting the DRM requirements. The higher orbits proposed in some of the DRMs may
seriously stretch the limits of capability of the RCS / OMS thrusters in the event of main
engine failure. This is probably an unlikely scenario but one that could occur. Several
peroxide transfers might be required in some cases, which might not only overstress the
duration capability of some thrusters but might exceed the limits of the pressurization
system as defined in the requirements.
Several telecons led to refinement of the half-dozen or so proposed DRMs down to two,
the first one representing a minimum orbital checkout {DRM-1 ) and the second
63
JRF Engineering SerxicesX-37 Monthly Report 1 Sept. 2001
Page 3
representing a mission of significant duration and delta-V that would demonstrate some
of the operational potential of the vehicle and its derivatives (DRM-2).
The Trade Study was divided into tv,o parts "'Trade A'" and "Trade B". The ti_rmerreferred to DRM-1 and the latter to DRM-2.
Significant discussion dealt v,ith modification of the weighting factors. The final factorsseemed reasonable.
Several propulsion options v,ere developed for X-37 including the baseline, hydrogen
peroxide monopropellant options, options using NTO and hydrazine and/or MMH in
various arrangements and hydrazine monopropellant. The peroxide monopropellant
options appear to be unable to do the more demanding DRM-2 and thus are not, in my
opinion, of much interest. The conventional storable bipropellants probably offer some
performance advantage over the baseline because of the relatively poor performance of
the AR2-3 main engine. (Note that this advantage will largely disappear with the
availability of higher performance 98c7c peroxide engines such as are now in
development). The hvdrazine monopropellant version will probably satisfy the DRMs but
has no growth potential. It is basically a dead end.
A point of some mild controversy in evaluating these options is hov, to credit the total
performance capability,, i.e. what can a given system do beyond just satisfying the
DRMs? This is a bit touchy since many would argue that there need be no capability
beyond just meeting the most demanding DRM. However, if this and cost are the only
criteria, it could easily lead us to a limited capability, dead end system. If there is to be
some possibility of a future use for the X-37 OV then more capability is desirable. To this
end. an evaluation criterion line item concerning maximum delta-V capability is to be
included.
The number of options was steadily reduced during the series of telecons. It was
temporarily decided that there was no particular point in carrying the baseline
bipropellant to do DRM-1 since the monopropellant systems can do it handily. However,
this decision was later reversed and a reduced propellant version of the baseline, dubbed
H-1A, was included for DRM-1 To keep the number of options under control, the other
options for DRM -1 were reduced to those that are capable of meeting the DRM
requirements but without a huge excess of performance. Similarly, for DRM-2 the team
worked to eliminate options that. by inspection, cannot meet the DRM and also those
that, while they meet the requirement, are less desirable because of excess complexity orsome other reason.
As a result, DRM-1 options are pretty much reduced to peroxide or hydrazine
monopropellant options in addition to the reduced capacity baseline. The DRM-2 options
are primarily bipropellant although the hydrazine monopropellant is an option. This
points up the disparity in performance of 90% peroxide versus hydrazine as a
monopropellant. The case for peroxide gets better with a higher proof but it will never be
_4
JRF Engineering Serx'icesX-37 Monthly Report 1 Sept. 2001
Page 4-
quite as good a monopropellant as hvdrazine. The various storable options involve
bipropellant RCS or hvdrazine monopropellant RCS. Both hvdrazine and MMH v, ere
originally' considered for the MPS. However the choice was made to use options that used
NTO and hvdrazine in the NIPS and monopropellant hvdrazine thrusters for RCS as the
simplest approach.
The chosen options were refined to support the propulsion trade studies. As of this report.
we are carrying three options for each DRM. In both cases, the peroxide baseline (using
the AR2-3_ is included, referred to as H-1 A for DRM-1. B for DRM-2. is included. For
DRM-1 the other two are H-3A: a multiple RCS tank H:O., system and S-3A: a single
tank N:l-ta system. For DRM-2. the other two are S-2B: an N_,H4/NTO bipropellant
system with N:H., monopropellant RCS and S-3B: a multiple tank N:H._ monopropellantsystem.
Boeing has done estimates of the weight reductions inherent in each option relative to thebaseline H-1. These estimates are -663 lb for H-3A. -729 lb for S-3A. -478 lb for S-3B.
and -559 for S-2B. Recall that these numbers are very preliminary. It is also well to
remember that these are not equal performers but for most. simply meet the DRM
requirements.
MSFC has assembled a x'ery good preliminary, list showing a subsystem testing approach.
While obviously more depth is needed this is a good start. It brings up the issue that
facility (or at least non-flight) tanks may be substituted for flight tanks in many cases.
The general feeling seems to be that this option applies mostly' to the non-peroxide
options, an assumption that may justin, a second look.
A significant point of discussion is the need for fidelity in ground test systems to support
development of the various propulsion system types. This function is supported in the
baseline by' the planned brassboard. It is suggested by the list discussed above and in
other discussions that some of the options need a less elaborate system. This may well be
true but we must be careful not to favor the newer system concepts by over optimism.
Preliminary Results of Trade Studies
I question why Material Compatibility is rated so poorly for the peroxide options. There
is an extensive database on such issues. Admittedly, some of the data are not as modern
as that for hydrazine but there is still significant information. This makes it sound as if
there was none.
While the gauging accuracy and reliability for peroxide is probably inferior to that for the
other propellants, is it really as bad as indicated?
What is the basis for the assumption that all peroxide systems need active pressure
control while the others use regulators? True, the Baseline is designed that way and it
65
JRF Engineering Serx'icesX-37 Monthly' Report I Sept. 2001
Page 5
may be justified for the complex propellant transfers and such {although 1 can see a x_a\
to do it with on/off valves and regulators) but I'm not sure it holds true for H-3A.
H-I and S-2B are stated to require the same turnaround time but H-1 is construed as less
desirable. Why? Better justification is needed.
I have some difficulty' seeing the large plume of the AR2-3 as being a significant factor.
It seems to me that the main v,orry about plume impingement will come from the RCS
thrusters and. in that case. peroxide is more benign.
Trade Study Thou_,hts
This is largely, a subjective opinion but I do not see H-3A and S-3B being greatly' superior
in terms of schedule, particularly, H-3A.
I question H- 1 being substantially lower than H-3A in terms of development risk. The
AR2-3 seems relatively lov, risk at this point. Concerns about peroxide transfer from
main to RCS tanks are valid and this may reduce the desirability' of H- l.
I think the traceability of S-3A and S-3B is very low. No operational vehicle is likely to
use either scheme so what is being traced to what? 1 do not feel that H-3A is very high bv
the same logic but it does advance peroxide technology so some credit for that is
probably' valid. S-2B at least has the virtue that such a system could be used in an
operational system if the decision goes against peroxide.
Cost Savine
I have reviewed the cost saving document generated as part of the trade study and find no
problem with the items listed. I assume Boeing has done enough homew'ork to validatethe numbers.
Propulsion Concept Evaluation
In addition to the Propulsion Trade Study telecons, I was asked to review a set of
documents (Opening Remarks, Popp Status Expanded, and Risk Factors 6-4-01 )
regarding the concerns of the MSFC propulsion community regarding the use of the
hydrogen peroxide / JP propellant combination in the X-37. I was asked to comment on
these documents partly as a result of my strong support of continuing with the baseline
system as opposed to the proposed development of systems using conventional storables.
In summary, my response is that I have no major disagreement with the concerns raised
by MSFC propulsion. There is serious w'ork to be done. Much of the work about which
they express concern would also have to be done with the proposed replacement systems
66
JRF Engineering ServicesX-37 Monthly Report 1 Sept. 2001
Page 6
and much that has already been done on the baseline v_ould have to be repeated if x_e
sv,itched to another approach. Any saving of money or schedule is doubtful at best. More
to the point, hov,,ever, and this has been my real point of contention all along, the
program was originally, proposed with the idea of bringing peroxide / JP technology' up to
speed in order to offer a non-toxic, non-carcinogenic alternative to current storables. If
v,'e drop this aspect of the program, we lose a major technology contribution and.
incidentally', one in which the USAF has substantial interest. NASA is supposed to be in
the business of advancing technology', not doing things we already, know how to do.
_7
JRF ENGINEERING SERVICES4023 Shadow Run
Las Cruces, NM 88011
(505) 532-9572 (phone/fax)e-mail: [email protected]
To:
From:
Subject:
Edgar W. NicksJim French
Weekly Report for 15 September 2001
15 September 2001
C: S. Turner. Lt. Col. Johannessen, M. Harris, J. Sisk, A. Nolen. T. Taylor. S. Stev, art.Lt. Col. Kastenholz
X-37
Pro_,ram
With the Air Force decision not to participate in the X-37 program and with no launch
vehicle being apparently available, there is very little to do pending a decision as to
whether the X-37 program will go forw'ard and, if so. in what form.
Because of the uncertainty of the situation, I have had no contact with Boeing for several
weeks. This week I decided to make a few telephone contacts simply to sample the
situation and to maintain such contacts as remain. It appears that, as of today, Boeing is
cutting back to an approximate 50 person level. This is apparently based upon the
assumption that whatever continuation program is developed will be at that level.
Apparently the GN&C and software groups are being retained at about their current level
but most other areas are being sharply reduced. Flight Sciences will be reduced to one
person. This reflects the fact that most of the subsonic aero is done and there is unlikely
to be any immediate need for higher speed data. While the propulsion personnel have
received no official word at this point, they read the signs as indicating that there will be
no propulsion whatever on the vehicle in the new program and are anticipating that theywill move on.
There were no telecons or other activities regarding the trade studies. It seems likely that,
given present circumstances, the trade studies are no longer of interest and will notcontinue.
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1, AGENCY USE ONLY (Leave I 2. REPORT DATE ! 3. REPORT TYPE AND DATES COVEREDblank) I 9 30_01 i WBS 4._.,.._ _ _ FinalRe_ort_ , i0 1 _. - _. __0 Jl
4. TITLE AND SUBTITLE 5. FUNDING NUMBERS
Final Report, "Pathfinder Technologies Specialist, X-37" NAS8-9906_
6. AUTHOR(S)James R. French
7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES)
SAIC
6725 Odxsse3 Drive
Huntsville. ,,M. 35806
9. SPONSORING / MONITORING AGENCY NAME(S) AND ADDRESS(ES)
NASA
George C Marshall Space Flight Center
Marshall Space Flight Center. ,M_, 35812
8. PERFORMING ORGANIZATIONREPORT NUMBER
NAS8-99060. "_VBS 4.1 ...."_ _
10. SPONSORING / MONITORINGAGENCY REPORT NUMBER
11. SUPPLEMENTARY NOTES
12a. DISTRIBUTION / AVAILABILITY STATEMENT 12b. DISTRIBUTION CODE
13. ABSTRACT(Maximum200 Words)The X-37 vehicle is a technology demonstrator sponsored by NASA. it includes a number of
experiments both imbedded (i.e., essential aspects of the vehicle) and separate. The
technologies demonstrated will be useful in future operational versions as well as having
broad applications to other programs. Mr. James R. French, of JRF Engineering Services
and as a consultant to SAIC, has provided technical support to the X-37 NASA Program
Office since the beginning of the program. In providing this service, Mr. French has
maintained close contact with the Boeing Seal Beach and Rocketd_me technical teams via
telephone, e-mail, and periodic visits. His interfaces were primarily with the working
engineers in order to provide NASA sponsors with a different view than that achieved
through management channels. Mr. French's periodic and highly detailed technical reports
were submitted to NASA and SAIC on a weekly/monthly basis. These reports addressed a wide
spectrum of programmatic and technical interests related to the X-37 Program including
vehicle design, flight sciences, propulsion, thermal protection, Guidance Navigation &
Control (GN&C), structures, and operations. This deliverable is presented as a
ccnsolidation of the twelve monthly reports submitted during the Contrac['s Option Year 2.
14. SUBJECT TERMS 15. NUMBER OF PAGES70
16. PRICE CODE
17. SECURITY CLASSIFICATION 18. SECURITY 19. SECURITY CLASSIFICATION 20. LIMITATION OF ABSTRACTOF REPORT CLASSIFICATION OF ABSTRACT
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